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Telecommunications
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IP Telephony Equipment
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Voice Gateway Transmission Requirements
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SP-3-4826-RV2 (to become ANSI/TIA-912-B)
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With corrections per ballot comments
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
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TABLE OF CONTENTS
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TABLE OF CONTENTS ..................................................................................................................... I
4
1
INTRODUCTION ......................................................................................................................... 1
5
6
1.1
1.2
General .................................................................................................................................. 1
Purpose.................................................................................................................................. 1
7
1.3
Categories of Performance Criteria ...................................................................................... 1
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2
SCOPE ........................................................................................................................................... 2
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2.1
2.2
Compliance Reference Point ................................................................................................ 2
Compliance Interpretation .................................................................................................... 2
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2.3
Regulatory Issues .................................................................................................................. 2
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3
NORMATIVE REFERENCES.................................................................................................... 3
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4
DEFINITIONS, ABBREVIATIONS AND ACRONYMS......................................................... 4
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4.1
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4.2 Insertion Loss Definition ...................................................................................................... 4
4.3 Sound Pressure Level Definition .......................................................................................... 4
4.4 0 dBr Point Definition .......................................................................................................... 4
4.5 Loudness Rating Definitions ................................................................................................ 4
4.5.1
Loudness Rating ............................................................................................................ 4
4.5.2
Relationship between Loudness Ratings and Loss Plans .............................................. 5
4.5.3
Half-Channel Send and Receive Loudness Rating (SLRHC and RLRHC)...................... 8
4.6 Port Definitions ..................................................................................................................... 8
4.7 Port Descriptions .................................................................................................................. 8
4.7.1
ONS – On Premise Station ............................................................................................ 8
4.7.2
OPS – Off Premise Station ............................................................................................ 8
4.7.3
DGS – Digital Station.................................................................................................... 9
4.7.4
WAN – Wide Area Network ......................................................................................... 9
4.7.5
PAL – Packet Access Line ............................................................................................ 9
4.7.6
DAL – Digital Access Line ........................................................................................... 9
4.7.7
FXO – Foreign Exchange Office ................................................................................... 9
4.7.8
FXD – Foreign Exchange Digital .................................................................................. 9
4.7.9
ATT – Analog Tie Trunk .............................................................................................. 9
4.8 Abbreviations and Acronyms ............................................................................................. 11
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Voice Gateway Definition .................................................................................................... 4
PREAMBLE ................................................................................................................................ 12
35
5.1
General ................................................................................................................................ 12
36
5.2
Reference Impedance .......................................................................................................... 12
37
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LOSS AND LEVEL PLANS ...................................................................................................... 13
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6.1
6.2
Introduction ......................................................................................................................... 13
Port-to-Port Loss Allocation ............................................................................................... 14
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6.3
Digital Padding ................................................................................................................... 14
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6.4
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6.5 Full-Channel Loss and Level Plan Requirements ............................................................... 15
6.5.1
Insertion Loss Criteria for Voice Gateways ................................................................ 15
6.5.2
Port-to-Port Loss Table Interpretation ........................................................................ 15
6.5.3
Port-to-Port Loudness Ratings Table Interpretation ................................................... 15
6.5.4
Voice Gateway Loss Ranges ....................................................................................... 15
6.5.5
ANSI/TIA-968-A and ANSI/TIA-968-A-1 Requirements .......................................... 15
6.6 Half-Channel Loss and Level Plan ..................................................................................... 19
6.6.1
Overview ..................................................................................................................... 19
6.6.2
Concept ........................................................................................................................ 19
6.6.3
Principle of Operation ................................................................................................. 19
6.6.4
Applicability ................................................................................................................ 20
6.6.5
Recommended Loss Ranges ........................................................................................ 20
6.6.6
Packet Network Losses................................................................................................ 20
6.6.7
Half-Channel Loss Plan Table .................................................................................... 21
6.6.8
Network Stability......................................................................................................... 22
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LOSS PARAMETERS ............................................................................................................... 23
7.1 Frequency Response ........................................................................................................... 23
7.1.1
Rejection of Power Line Interference ......................................................................... 23
7.2 Tracking Error and Overload Compression ........................................................................ 23
7.2.1
Tracking Error ............................................................................................................. 23
7.2.2
Overload Compression ................................................................................................ 26
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Voice Gateway Loss Plan Assumptions ............................................................................. 14
ECHO CONTROL AND RETURN LOSS ............................................................................... 27
8.1
8.2
9
Hybrid Balance Requirements ............................................................................................ 27
Input Impedance Requirements .......................................................................................... 28
NOISE AND DISTORTION IMPAIRMENTS ........................................................................ 30
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9.1 Idle-Channel Noise ............................................................................................................. 30
9.1.1
3 kHz Flat Noise .......................................................................................................... 30
9.1.2
C- Message Weighted Noise ....................................................................................... 30
9.2 Longitudinal Balance .......................................................................................................... 31
9.2.1
Longitudinal-to-Metallic Balance ............................................................................... 31
9.2.2
Metallic-to-Longitudinal (Transverse Balance) Balance ............................................ 32
9.3 Crosstalk ............................................................................................................................. 33
9.3.1
Requirement ................................................................................................................ 33
9.4 Quantization Distortion ...................................................................................................... 33
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9.5
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10
Single-Frequency Distortion ............................................................................................... 33
OTHER IMPAIRMENTS ....................................................................................................... 34
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10.1 Intermodulation Distortion ................................................................................................. 34
10.2 Envelope Delay ................................................................................................................... 35
10.2.1 Definitions ................................................................................................................... 35
10.2.2 Relative Envelope Delay (RED) Requirements .......................................................... 35
10.3 Impulse Noise ..................................................................................................................... 37
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10.4 Jitter .................................................................................................................................... 37
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10.5 Gain Hit............................................................................................................................... 37
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10.6 Phase Hit ............................................................................................................................. 37
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10.7 Dropout ............................................................................................................................... 37
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10.8 Peak-to-Average Power Ratio ............................................................................................. 37
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SIGNAL LEVELS.................................................................................................................... 38
6
ANNEX A
(INFORMATIVE) - MEASUREMENT GUIDELINES ........................................ 39
7
A.1
Gain Ripples in the Measurement Path .............................................................................. 39
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A.2
A.3
Transmission Level Translation ......................................................................................... 39
Dial-up Port for Trunk Testing ........................................................................................... 39
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A.4
A.5
Digital Test Port Availability.............................................................................................. 39
Hybrid Balance ................................................................................................................... 40
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A.6
Input Impedance .................................................................................................................. 40
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A.7
A.8
Idle Channel Noise .............................................................................................................. 44
Longitudinal Balance .......................................................................................................... 45
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A.8.1 Longitudinal to Metallic Balance ....................................................................................... 45
A.8.2 Metallic to Longitudinal (Transverse) Balance .................................................................. 45
A.8.2.1 Transverse Balance Test (Analog) .............................................................................. 46
A.8.2.2 Transverse Balance Test (Digital) ............................................................................... 49
A.9. Crosstalk Coupling Loss ..................................................................................................... 50
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ANNEX B
(INFORMATIVE) - TELEPHONY LOSS LEVEL PLANNING OVERVIEW . 52
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B.1
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B.2 Send and Receive Levels .................................................................................................... 52
B.2.1 Telephone Equipment Loudness Ratings ........................................................................... 53
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B.2.2
B.2.3
B.2.4
B.3
B.4
Overall Loudness Ratings ................................................................................................... 53
Optimum Overall Loudness Ratings ................................................................................... 54
ATT Network Interface Loudness Ratings ......................................................................... 55
Port-to-Port Loss Allocation ............................................................................................... 55
DTMF Overload on Analog Trunks ................................................................................... 56
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B.5
B.6
Open Loop Loss and Network Stability ............................................................................. 57
Reference Levels................................................................................................................. 57
31
B.6.1 Zero-Level Point ................................................................................................................. 57
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B.6.2 0 dBm0 Definition .............................................................................................................. 57
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B.6.3 Digital Milliwatt ................................................................................................................. 57
B.6.4 Transmission Level Translation ......................................................................................... 57
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Introduction ......................................................................................................................... 52
ANNEX C
C.1
C.2
C.3
(INFORMATIVE) - LOSS DEFINITIONS ............................................................ 59
Echo Return Loss (ERL)..................................................................................................... 59
Return Loss (RL) ................................................................................................................ 60
Transhybrid Loss (THL) ..................................................................................................... 60
ANNEX D
(INFORMATIVE) - PAN-EUROPEAN LOSS AND LEVEL PLANS - ES 202 020
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D.1
The Pan-European Half-Channel Loss Plan ....................................................................... 61
2
3
4
D.1.1 Voice Gateway Connections ............................................................................................... 61
D.1.2 Interface Descriptions ......................................................................................................... 62
D.1.3 Voice Gateway Half-Channel Loss Plan ............................................................................ 62
5
D.2
The Pan-European Full-Channel Loss Plan ........................................................................ 64
6
7
ANNEX E
(INFORMATIVE) - LOSS PLAN AND LOUDNESS RATING REFERENCES AND
HIERARCHY 65
8
ANNEX F
(INFORMATIVE) - IP TRANSMISSION IMPAIRMENTS................................ 66
9
F.1
Delay ................................................................................................................................... 66
10
F.2
Packet Loss ......................................................................................................................... 66
11
F.3
Voice Gateways and Network Performance ....................................................................... 66
12
F.4
Voice Quality of Service..................................................................................................... 67
13
14
ANNEX G
(INFORMATIVE) - BIBLIOGRAPHY .................................................................. 68
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SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
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FOREWORD
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(This foreword is not part of this standard.)
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This document is a TIA Telecommunications Standard produced by Subcommittee TR-41.4 of
Committee TR-41. This standard was developed in accordance with TIA procedural guidelines, and
represents the consensus position of the Subcommittee, which also served as the formulating group. This
standard is based on ANSI/TIA-912-A.
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The TR-41.4 IP Telephony Infrastructures Subcommittee acknowledges the contribution made by the
following individuals in the development of this standard.
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Name
Roger Britt
Richard Frank
Richard Hatherill
Dorothy Lockard
Joachim Pomy
Kirit Patel
Tailey Tung
Representing
Nortel
Dietrich Lockard Group
Maxxeon
Dietrich Lockard Group
Avaya
Cisco Systems
Siemens ICN
Previous
Versions
TIA-912-B
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The European version of this joint work is the "Harmonized Pan-European/North-American approach to
loss and level planning for voice gateways to IP based networks" standard. Within ETSI it has the
number ETSI ES 202 020 V1.4.1.
There are seven annexes in this standard.
Suggestions for improvement of this standard are welcome. They should be sent to:
Telecommunications Industry Association
Engineering Department
Suite 300
2500 Wilson Boulevard
Arlington, VA 22201
( http://www.tiaonline.org )
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Introduction
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1.1 General
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Advances in digital voice communications over packet channels such as the Internet and Local
Area Networks have made it necessary to create a transmission standard for IP (Internet
Protocol) Telephony systems. The term coined for these IP Telephony systems is “Voice
Gateway” (VG), which is the equivalent to the term PBX as used for traditional time-divisionmultiplexed (TDM) systems. PBX requirements are specified in ANSI/TIA-464-C and its
addendum, ANSI/TIA-464-C-1.
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1.2 Purpose
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This standard establishes performance and technical criteria for interfacing and connecting with
the various elements of public and private telecommunications networks. Compliance with these
requirements should assure quality service.
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This standard is intended to be coordinated with the public network loss plan according to the
principles of ITU-T Recommendation G.101 and ANSI T1.508 and to fully comply with the
regulatory requirements of ANSI/TIA-968-A and its addendum, ANSI/TIA-968-A-1.
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Voice quality-of-service issues such as the impact of transmission delay, speech compression and
packet loss are addressed in TIA/EIA/TSB32-A and TIA/TSB116-A.
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This standard was also developed in conjunction with ETSI TC STQ, who generated an
equivalent half-channel loss plan standard, ETSI ES 202 020, for VGs that is harmonized with
this standard.
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1.3 Categories of Performance Criteria
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Four types of requirements are specified in this standard: Mandatory, Recommended, Permissive
and Advisory:
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Mandatory requirements are designated by the terms “shall” and “shall not”. These
requirements are used to indicate conformity in which no deviation is permitted.
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Recommended requirements are designated by the terms “should” and “should not”. These
requirements generally relate to compatibility or performance advantages toward which
future designs should strive.
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Permissive requirements are designated by the terms “may” and “may not”. These requirements
are used to indicate an action that is permitted within the limits of the standard.
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Advisory requirements are designated by the term “desirable”. Advisory criteria represent
product goals or are included in an effort to ensure universal product compatibility and may
be used instead of a recommended requirement. If both a mandatory and an advisory level
are specified for the same criterion, the advisory level represents a goal currently identifiable
as having distinct compatibility or performance advantages toward which future designs
should strive.
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Scope
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This standard covers the transmission requirements and specifically the loss plan for VGs. For
the purposes of this standard, a VG is considered to be a device that performs voice routing
functions between:
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
Telephones;
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
Public and private networks;
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
Packet-based networks1.
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VGs include, but are not limited to:
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
Packet-based Enterprise equipment that is functionally equivalent to a TDM-based PBX;
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
Residential Gateways;
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
Voice-over-ADSL Integrated Access Device (IAD);
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
Voice-over-Cable Multimedia Terminal Adaptor (MTA).
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Telephones referred to in this standard are assumed to comply with the requirements specified in:
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
ANSI/TIA-470.110-C for analog telephones, or
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
ANSI/TIA-810-B for digital telephones.
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2.1 Compliance Reference Point
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The reference point for this standard is determined at the VG interface boundaries and is not to
be construed as a constraint on the internal coding or switching techniques of the VG.
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2.2 Compliance Interpretation
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A VG complies with this standard when it conforms to the requirements applicable to the
interfaces with which it is equipped.
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2.3 Regulatory Issues
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This standard is intended to be in conformity with ANSI/TIA-968-A and its addenda regarding
network harm, but is not limited to the scope of this standard. In the event that the ANSI/TIA968-A and its addenda requirements are more stringent than those contained in this standard, the
provisions of ANSI/TIA-968-A and its addenda apply.
1
For historical reasons, the terms “IP” and “IP-based networks” are used extensively in this
standard in a generic fashion, but the more generic terms “packet” and “packet-based
networks” are now more appropriate. While it is not practical to replace every instance of “IP”
with “packet” in this standard, it is the intent of this standard that “IP” and “packet” have the
same generic meaning.
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SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
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Normative References
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The following standards and recommendations contain provisions, which are referenced in this
document. At the time of publication, the editions indicated were valid. All standards are subject
to revision, and parties to agreements based on this document are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. ANSI and TIA
maintain registers of currently valid national standards published by them.
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[1]
ANSI T1.508 (2003), Loss Plan for Evolving Digital Networks.
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[2]
ANSI/TIA-464-C-2002, Requirements for PBX Switching Equipment.
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[3]
ANSI/TIA-464-C-1-2004, Requirements for PBX Switching Equipment – Addendum 1.
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[4]
ANSI/TIA-470.110-C-2004, Handset Acoustic Performance Requirements for Analog
Telephones.
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[5]
ANSI/TIA-810-B-2006, Transmission Requirements for Narrowband Digital Telephones.
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[6]
ANSI/TIA-968-A-2002, Technical Requirements for Connection of Terminal Equipment to
the Telephone Network.
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[7]
ANSI/TIA-968-A-1-2003, Technical Requirements for Connection of Terminal Equipment
to the Telephone Network – Addendum 1.
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[8]
ITU-T Recommendation G.101 (11/03), The transmission plan.
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[9]
ITU-T Recommendation G.122 (03/93), Influence of National Systems on Stability and
Talker Echo in International Connections.
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[10] ITU-T Recommendation G.711 (11/88), Pulse Code Modulation (PCM) of Voice
Frequencies.
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[11] ETSI ES 202 020 V1.4.1 (2006), Harmonized Pan-European/North-American approach to
loss and level plan for voice gateways to IP based networks.
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Definitions, Abbreviations and Acronyms
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For the purposes of this standard, the following definitions, abbreviations and acronyms apply.
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4.1 Voice Gateway Definition
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A device which routes packetized voice from one end-point to another, and provides other voice
related functions that a data gateway would not provide, e.g., voice coding and/or compression
and echo cancellation.
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Its function is analogous to a PBX in that it provides connectivity between customer premise
voice terminals. It may provide interfaces to analog and digital (TDM and IP) voice terminals,
and access to both public and private WANs and public and private switched telephone
networks.
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4.2 Insertion Loss Definition
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The insertion loss of a VG connection is defined as the 1 kHz level difference between the power
delivered from a source connected across an input port to the power delivered to a measuring
instrument connected across an output port.
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Both the signal source and the measurement instrument are assumed to have an impedance of
600  at 1 kHz.
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The insertion loss values are expressed as an absolute loss in dB between interface ports.
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4.3 Sound Pressure Level Definition
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Sound pressure level is a value expressed as a ratio of the pressure of a sound to a reference
pressure. The following sound level units are used in this standard:
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dBPa:
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dBSPL: The sound pressure level, in decibels of a sound is 20 times the logarithm to the base
10 of the ratio of the pressure of this sound to the reference pressure of
2 X 10-5 N/m2 (0 dBPa = 94 dBSPL).
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4.4 0 dBr Point Definition
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From this standard’s loss plan perspective, the 0 dBr point is any point in the digital network.
The “r” refers to the term “relative”, but unlike some loss plans, the loss plan in this standard is
absolute, not relative, so the concept of relative levels is not used. Note: more rigorous
definitions of the 0 dBr point may be required for other applications, e.g., for use with the EModel.
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4.5 Loudness Rating Definitions
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4.5.1 Loudness Rating
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Loudness ratings are a function of the acoustic/electrical conversion characteristics of the
originating and terminating equipment (typically telephones). These ratings are determined by
measuring the conversion characteristics over the telephony frequency band and by applying a
weighting factor for each third octave band.
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These loudness ratings are defined as the Send Loudness Rating (SLR) and Receive Loudness
Rating (RLR), and the sum of these ratings (plus any circuit gain or loss) is defined as the
Overall Loudness Rating (OLR).
The sound pressure level, in decibels of a sound is 20 times the logarithm to the base
10 of the ratio of the pressure of this sound to the reference pressure of
1 Pascal (Pa). Note: 1 Pa = 1 N/m2.
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The following convention is used in this standard when referring to loudness ratings:
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
The Send Loudness Rating (SLR) and Receive Loudness Rating (RLR) are collectively
referred to as the Loudness Rating (LR).
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The loudness ratings are given in the order SLR and RLR, i.e., a digital telephone with an
SLR of 8 dB and RLR of 2 dB would be designated as having an LR of 8 and 2.
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4.5.2 Relationship between Loudness Ratings and Loss Plans
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In order to understand the relationship between loudness ratings and loss plans, five basic fullchannel scenarios are illustrated in Figures 1 to 5. Although these scenarios are simple, they can
easily be applied to more complicated scenarios because the digital network is lossless and many
combinations of TDM or IP networks can be inserted into the diagrams at the half-channel 0 dBr
point, without affecting the end-to-end loss plan because the loss plan should only be applied at
the edge of the network.
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Each diagram follows the same format. On the left and right hand edges are either analog or
digital telephones. Figure 1 illustrates the simplest example, two digital sets connected to a Voice
Gateway. Starting in the top left corner, the SLR of the digital set is 8 dB. It is highlighted in
bold because the 8 dB is an important standards requirement in ANSI/TIA-810-B, as identified in
the yellow tab. Moving towards the center 0 dBr point, the half-channel SLR, SLRHC, remains at
8 dB, because there is no loss in the digital path including the upper left Tx pad of the DGS port
(as specified in this standard) in the VG. For loss planning purposes, the “Terminal” label
extends to the edge of the VG to be consistent with analog sets, whose loudness ratings include
the copper line. Note: The VG loss plan is specified in Clause 6.
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RLR works in a similar manner, but it is evaluated from right-to-left towards the 0 dBr point. The
set RLR is 2 dB, the loss plan, i.e., Rx pad in the upper right of the VG, is 0 dB, so the halfchannel RLR, RLRHC, just to the right of the 0 dBr point, is still 2 dB. The optimum OLR of 10
dB for this upper connection is shown in the green box on the right hand side. It is calculated by
adding the upper SLRHC to the upper RLRHC, i.e., OLR = 8 + 2 = 10 dB. The bottom connection
from the right digital set to the left digital set is evaluated the same way and in this case is
symmetrical.
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Figure 1 – Scenario 1: Digital Set-VG-Digital Set
Terminal
TIA-810-B
SLR
8 dB
0 dB
Digital
10 dB
OLR
Set
0 dB
2 dB
RLR
TIA-810-B
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Digital Line
Public/Private Network
TIA-912-B TIA-912-B
SLRHC
RLRHC
8 dB
2 dB
Tx pad
Rx pad
0 dB
0 dB
DGS VG DGS
0 dB
0 dB
Rx pad
Tx pad
2 dB
8 dB
RLRHC
SLRHC
TIA-912-B TIA-912-B
0 dBr
Terminal
TIA-810-B
RLR
2 dB
0 dB
Digital Line
Digital
OLR
10 dB
Set
0 dB
8 dB
SLR
TIA-810-B
Figure 2 illustrates a basic analog set connection with two analog sets connected, both with 0 km
loops, to the same Digital End Office (DEO). Analog sets may or may not have loop
compensation (shortened to “loop comp” in the diagrams). This feature is only applicable to
short DEO lines. A detailed explanation of loop compensation is documented in Annex E of
ANSI/TIA-470.110-C. Since the telephone in Figure 2 does not have any loop compensation loss
(0dB), the OLR is quite loud at 3 dB. However, some telephones do have loop compensation and
these telephones will have better, i.e., quieter, OLRs. Theoretically, DEOs should be able to
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SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
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detect very short loops like this and apply extra electrical loss to compensate for the lack of
copper loss.
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The loudness ratings of analog sets are determined acoustically at the handset and electrically at
a termination that is the equivalent of the line card of a DEO, In addition, the LRs are usually
specified at several different line lengths, meaning that the terms SLR and RLR include the
copper line. So Figure 2 introduces the terms SLRT and RLRT for the loudness ratings of the
telephone without the copper line, where the subscript ‘T’ refers to a telephone without the
copper line, e.g., a 0 dB line. The SLRT of 4 dB and RLRT of -7 dB are specified in ANSI/TIA470.110-C as the SLR and RLR (bold 4 dB and -7 dB, respectively) for the 0 dB line. In addition,
Annex E of ANSI/TIA-470.110-C describes this in more detail.
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The DEO loss plan is specified in ANSI/T1.508-2003 and it is 0 dB in the send direction and
6 dB in the receive direction. So at the 0 dBr point, the SLRHC remains at 4 dB, but the RLRHC
changes to -1 dB from RLR -7 dB, due the 6 dB Rx pad. The connection is symmetrical, so the
OLR is 3 dB in both directions, i.e., OLR = 4-1 = 3 dB.
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Figure 2 – Scenario 2: Analog Set-DEO-Analog Set (0 km)
Terminal
TIA-470.110-C
SLR
4 dB
Anx E
SLRT
4 dB
0 dB
3 dB
OLR
Analog
Loop
Set
Comp
0 dB
-7 dB
RLRT
Anx E
0 dB
0 km PSTN
Subscriber Line
0 dB
-7 dB
RLR
TIA-470.110-C
Public Network
T1.508
T1.508
SLRHC
RLRHC
4 dB
-1 dB
Tx pad
Rx pad
0 dB
6 dB
AAL DEO AAL
6 dB
0 dB
Rx pad
Tx pad
-1 dB
4 dB
RLRHC
SLRHC
T1.508
T1.508
0 dBr
Terminal
TIA-470.110-C
RLR
-7 dB
0 dB
0 km PSTN
Subscriber Line
0 dB
Anx E
RLRT
-7 dB
0 dB
Loop
Analog
Comp
Set
OLR
3 dB
0 dB
4 dB
SLR
TIA-470.110-C
4 dB
SLRT
Anx E
16
17
18
19
20
Scenario 3 is similar to Scenario 2 except the loop in both directions is increased to the typical
length of 2.7 km or in terms of loss, 4 dB. As shown in Figure 3, the SLRHC is the optimum 8 dB
at the 0 dBr point, while the RLRHC of 3 dB is very close to the optimum 2 dB, based on the
RLRT of -7 dB plus the copper loss of 4 dB (RLR of -3 dB) and the DEO Rx loss pad of 6 dB.
21
Figure 3 – Scenario 3: Analog Set-DEO-Analog Set (2.7 km)
Terminal
TIA-470.110-C
SLR
8 dB
Anx E
SLRT
4 dB
0 dB
11 dB
OLR
Analog
Loop
Set
Comp
0 dB
-7 dB
RLRT
Anx E
22
23
24
25
26
4 dB
2.7 km PSTN
Subscriber Line
4 dB
-3 dB
RLR
TIA-470.110-C
Public Network
T1.508
T1.508
SLRHC
RLRHC
8 dB
3 dB
Tx pad
Rx pad
0 dB
6 dB
AAL DEO AAL
6 dB
0 dB
Rx pad
Tx pad
3 dB
8 dB
RLRHC
SLRHC
T1.508
T1.508
0 dBr
Terminal
TIA-470.110-C
RLR
-3 dB
4 dB
2.7 km PSTN
Subscriber Line
4 dB
8 dB
SLR
TIA-470.110-C
Anx E
RLRT
-7 dB
0 dB
Loop
Analog
Comp
Set
OLR
11 dB
0 dB
4 dB
SLRT
Anx E
Scenario 4 in Figure 4 is similar to Scenario 2 except the DEO in Scenario 2 is replaced with a
VG. In addition, there are a number of other changes: (a) the port designation at the line card
changes from AAL for the DEO to ONS for the VG, (b) the loudness rating specification for the
set changes to Annex E of ANSI/TIA-470.110-C because most VGs have different lines cards
6
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
2
3
4
compared to DEOs, (c) the loss plan changes from 0 dB and 6 dB in ANSI/T1.508 to 0 dB and 12
dB in this standard. The end result is an improved loss plan with an OLR of 9 dB because the VG
inserts 6 dB more loss in the Rx direction knowing that there is no copper loss between the set
and the VG.
5
6
7
8
9
10
11
At this point, it is worth explaining a subtle detail about the full-channel loss plans presented in
Clause 6.5. ONS to ONS connections, like Scenario 4, are specified with 12 dB of loss and are
shown in Figure 4 as 12 dB of loss in the receive direction. This may not be the optimum way to
partition the loss plan, but it is the only way that it can be specified in Table 1 and Table 2. An
alternative partitioning of the 12 dB is shown in the half-channel loss plan, Table 6, with 3 dB in
the send direction (Tx pad) and 9 dB in the receive direction (Rx pad). Scenario 5 will expand
more on this point. Also see Table 5, the last paragraph of Clause 6.6.1 and Annex B.4.
12
Figure 4 – Scenario 4: Analog Set-VG-Analog Set
Anx E
SLRT
4 dB
10 dB
OLR
Terminal
Public/Private Network
TIA-470.110-C Anx E TIA-912-B TIA-912-B
SLR
SLRHC
RLRHC
4 dB
7 dB
2 dB
Tx pad
Rx pad
0 dB
0 dB
3 dB
0 dB
Analog
Loop
Set
Comp
0 dB
-7 dB
RLRT
Anx E
Digital
0 km Line
Line
ONS VG DGS
0 dB
9 dB
0 dB
Rx pad
Tx pad
-7 dB
2 dB
8 dB
RLR
RLRHC
SLRHC
TIA-470.110-C Anx E TIA-912-B TIA-912-B
0 dBr
Terminal
RLR 810-B
RLR
2 dB
0 dB
Digital Line
Digital
OLR
9 dB
Set
0 dB
8 dB
SLR
SLR 810-B
13
14
15
16
17
18
19
20
21
22
The final example, Scenario 5, shown in Figure 5, is the required loss plan for most Residential
Gateways, like MTAs and IADs. This is because this type of VG generally has an ONS port on
one side and a digital port on the other. While the digital port in the example is connected to
digital set via a DGS port, in practice the digital port would be a PAL port. The loss plan for
PAL and DGS ports is identical, so Scenario 5 correctly illustrates the loudness ratings and loss
plan for the “typical” situation. The objective of most loss plans to present SLRHC 8 dB and
RLRHC 2 dB at the 0 dBr point. This is achieved in Scenario 5 within the limitations of the 3 dB
loss steps used by this standard. Be aware that is acceptable to fine tune the Tx pad to 4 dB, but it
is unnecessary because the tolerance on analog telephone loudness ratings is wide.
23
24
25
26
27
Note that if the 3 dB and 9 dB loss plan in Scenario 5 was applied to Scenario 4 the OLR results
would be the same. However, the loss partitioning in Scenario 5 has the advantage that the 3 dB
Tx pad replaces the missing copper line, which helps to produce the correct level to the DTMF
receiver in the VG. Similarly in the receive direction, Scenario 5 emulates Scenario 3 with the
9 dB partitioned as 3 dB copper line plus 6 dB for the DEO Rx pad.
7
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
Figure 5 – Scenario 5: Analog Set-VG-Digital Set
1
Anx E
SLRT
4 dB
10 dB
OLR
Analog
Loop
Set
Comp
0 dB
-7 dB
RLRT
Anx E
2
3
Terminal
Public/Private Network
TIA-470.110-C Anx E TIA-912-B TIA-912-B
SLR
SLRHC
RLRHC
4 dB
7 dB
2 dB
Tx pad
Rx pad
0 dB
0 dB
3 dB
0 dB
Digital
0 km Line
Line
ONS VG DGS
0 dB
9 dB
0 dB
Rx pad
Tx pad
-7 dB
2 dB
8 dB
RLR
RLRHC
SLRHC
TIA-470.110-C Anx E TIA-912-B TIA-912-B
0 dBr
Terminal
RLR 810-B
RLR
2 dB
0 dB
Digital Line
Digital
OLR
9 dB
Set
0 dB
8 dB
SLR
SLR 810-B
4
4.5.3 Half-Channel Send and Receive Loudness Rating (SLRHC and RLRHC)
5
6
7
The concept of 0 dBr can apply at any point in the digital connection path. A special case is the
VG-to-packet network connection point, as this is the reference point for all packet transmission
levels. The SLR at the 0 dBr point is defined as the SLRHC (Half-Channel SLR).
8
9
Similarly, for the packet network-to-VG connection point, the RLR at the 0 dBr point is defined
as the RLRHC (Half-Channel RLR).
10
11
See Clause 6.6 for further information on the half-channel loss plan and Annex B for further
information on loudness ratings.
12
4.6 Port Definitions
13
14
15
16
Figure 6 illustrates the connection types, and corresponding VG port definitions, for a typical VG
application. There may be other applications not covered by this diagram, but sufficient
information is provided for users to determine the applicable connection types for their particular
application, and the corresponding port losses to be applied.
17
18
19
Users should be aware that the port definition might only apply to the VG end of the connection,
as other entities could have a different port definition for the same connection. For example, the
VG FXO connection is defined as an AAL (analog access line) by the digital end office (DEO).
20
21
22
23
Note: Connections such as DAL, FXO, FXD, and ATT are generically referred to as trunks. This
term refers to connections between DEOs in the PSTN, and analogously is used to describe
connections between DEOs, PBXs, and VGs. It should also be noted that from a DEO and
T1.508 perspective, these VG trunks are called lines.
24
4.7 Port Descriptions
25
4.7.1 ONS – On Premise Station
26
27
28
29
30
An ONS interface is used for standard analog telephones, representative of 2500-type POTS
telephones, located on the same premises as the VG, and is the direct equivalent of the PBX ONS
connection. The termination is 600 ohms, the connection loss from the station to the VG is
typically low and the DC feed is usually a constant current supply that simulates a long loop. The
term FXS is sometimes used in place of ONS.
31
4.7.2 OPS – Off Premise Station
32
33
An OPS interface is used for standard analog telephones, representative of 2500-type POTS
telephones, not located on the same premises as the VG, and is the direct equivalent of the PBX
8
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
2
3
4
OPS connection. The termination is 600 ohms, the connection loss from the station to the VG is
typically significant and the DC feed is usually the same as a DEO (48 volts). This port is also
used for analog two-wire connections to remote VGs, PBXs and Key Systems, via a local DEO.
The term FXS is sometimes used in place of OPS.
5
4.7.3 DGS – Digital Station
6
A DGS interface is used for all digital telephones conforming to ANSI/TIA-810-B.
7
Note: This includes digital telephones based on both TDM and packet transmission.
8
4.7.4 WAN – Wide Area Network
9
10
11
A WAN interface connects from Enterprise VGs to packet-based wide area networks. The
transmission path within the WAN is entirely digital. The only distinction between a WAN port
and a PAL port is that the PAL port supports less bandwidth.
12
13
14
Note: The term WAN is used in the same context as PSTN, in that it represents connections
between geographically separated VGs. It should be noted that WAN and LAN are synonymous
from a transmission perspective.
15
4.7.5 PAL – Packet Access Line
16
17
18
A PAL interface connects from MTA or IAD VGs to packet-based wide area networks. The
transmission path within the PAL is entirely digital. The only distinction between a WAN port
and a PAL port is that the PAL port supports less bandwidth.
19
4.7.6 DAL – Digital Access Line
20
21
22
23
A DAL interface connects to all TDM-based digital network connections and it is the direct
equivalent of the PBX DAL interface. It should be noted that although the connection to the
public switched network may be digital, there is no guarantee that the end-to-end connection will
remain digital.
24
4.7.7 FXO – Foreign Exchange Office
25
26
An FXO interface is used for analog connections to a central office. It is equivalent to the PBX
term AAL(A), or analog access line (analog).
27
4.7.8 FXD – Foreign Exchange Digital
28
29
30
31
An FXD interface is used for digital connection, via a channel bank, to an analog access line
(AAL) of a DEO. It is equivalent to the PBX term AAL(D), or analog access line (digital). A loss
equivalent to the typical analog connection loss has to be inserted at the VG, as the channel bank
is located close to the DEO.
32
4.7.9 ATT – Analog Tie Trunk
33
34
35
36
An ATT interface is used for four-wire analog private network connections, typically via the
public network. This port also applies to two-wire VG interfaces that use an external four-wire
termination set (4WTS) to connect to the public network. PBX documents may either use the
same term, ATT, or the older term, A/TT.
37
9
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Figure 6 – Voice Gateway Port Definitions and Connections
2
Packe t Conne ction
Packet Facilities
(DEO, IDLC, VG)
TDM Conne ction
Analog Conne ction
PAL
WAN
PAL
WAN
Voice
Gateway
Packet Network Ports
DEO
PAL
PAL
WAN
WAN
DAL
DAL
DAL
DAL
DT
DAL
AAL
FXO
AAL CB
FXD
Public
Switched
Network
Ports
Voice
Gateway
Private
Network
Ports
(Enterprise,
MTA & IAD)
Telephone
Access Lines
OPS
OPS
ONS
DGS
PBX
DAL
DAL
ONS
AAL(A)
ATT
ATT
DGS
3
4
VG Port
Designation
Port Definition
PBX Port
Designation
ONS
DEO Port
Designation
AAL
ONS
Analog On Premise Station
OPS
Analog Off Premise Station - can be via an analog connection through a
DEO
OPS
AAL
DGS
Digital Station (telephone)
DGS
DAL
WAN
Wide Area Network (packet connection)
-
WAN
PAL
Packet Access Line (packet connection)
-
PAL
DAL
Digital Access Line - digital connection to a DEO
DAL
DAL
FXO
Foreign Exchange Office - analog connection to a DEO
AAL(A)
AAL
FXD
Foreign Exchange Digital - digital connection to a DEO via a channel
bank
AAL(D)
AAL
ATT
Analog Tie Trunk - private analog network connection to a gateway/PBX
ATT
ATT
10
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
4.8 Abbreviations and Acronyms
2
Abbreviations and acronyms, other than in common usage, are defined below.
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
AAL
AAL(A)
AAL(D)
A/D
ADSL
ATT
A/TT
BRL
CB
CO
D/A
DAL
DEO
DID
DGS
DMW
DT
FDM
FXD
FXO
FXS
IAD
IP
LAN
LR
MTA
OLL
OLR
ONS
OPS
PAL
PBX
PCM
PSTN
RLR
RLRHC
SLR
SLRHC
SPL
TDM
VG
WAN
Analog Access Line (Analog Interface at DEO)
Analog Access Line (Analog Interface at PBX)
Analog Access Line (Digital Interface at PBX)
Analog-to-Digital
Asynchronous Digital Subscriber Loop
Analog Tie Trunk (latest acronym format)
Analog Tie Trunk (previous acronym format)
Balance Return Loss
Channel Bank
Central Office
Digital-to-Analog
Digital Access Line
Digital End Office
Direct Inward Dialing
Digital Station
Digital Milliwatt
Digital Trunk
Frequency Division Multiplexing
Foreign Exchange Digital
Foreign Exchange Office
Foreign Exchange Station (see ONS & OPS)
Integrated Access Device
Internet Protocol
Local Area Network
Loudness Rating
Multimedia Terminal Adaptor
Open Loop Loss
Overall Loudness Rating
On Premise Station
Off Premise Station
Packet Access Line
Private Branch Exchange
Pulse Code Modulation
Public Switched Telephone Network
Receive Loudness Rating
Half-Channel Receive Loudness Rating
Send Loudness Rating
Half-Channel Send Loudness Rating
Sound Pressure Level
Time Division Multiplex
Voice Gateway
Wide Area Network
11
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
5
Preamble
2
5.1 General
3
4
Digital interfaces in the United States and Canada use -law encoding/decoding as defined in
ITU-T Recommendation G.711 (1988), ‘Pulse Code Modulation of Voice Frequencies’.
5
6
7
8
The transmission requirements contained in this standard are based on an industry-developed
fixed loss and level plan. The requirements were developed with the objective of maintaining or
improving the quality of service for connections within existing and evolving communication
networks.
9
10
11
The requirements contained in this standard are based on current understanding of required
performance and on the capabilities of present technology. As technology evolves, or as
performance needs change, these requirements may become subject to change.
12
13
Note: For historical reasons the terms Stations, Sets, Telephones, and Terminals are used
interchangeably in this standard.
14
5.2 Reference Impedance
15
16
Transmission requirements contained here apply with station and trunk interfaces terminated in a
nominal impedance of 600 , unless otherwise specified.
17
18
All measurements should be made at an equipment access point connected to the equipment by
no more than 15 meters of cable, unless otherwise specified.
12
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
6
Loss and Level Plans
2
6.1 Introduction
3
4
5
6
7
8
9
10
While this standard may appear to be a stand-alone document, it is not. Annex E best illustrates
how this standard fits into the hierarchy of transmission planning standards. ITU-T
Recommendation G.101 is at the top of the hierarchy and it provides the high level objectives for
this standard. It is the objective of this standard to comply with the fundamental principles of
transmission planning given in Clause 5 of Rec. G.101. In particular principle 5, which
recommends that the optimum end-to-end loudness be OLR = 10 dB, partitioned as SLR = 8 dB
and RLR = 2 dB on digital connections for optimum dynamic range, is the key objective of this
loss and level plan.
11
12
13
14
15
16
17
Another important objective for this loss plan is to economically minimize the effect of echo due
to signal reflections that are caused by impedance mismatching at 2-to-4 wire conversions in the
transmission path. In general, the insertion of loss in the transmission path reduces the
impairment due to echo, but increases the impairment due to noise. Another consideration that
must be taken into account is that insertion of too much loss will adversely affect customer
satisfaction with the received listening level. Therefore, rather than increasing loss indefinitely
on longer circuits, echo is controlled by the deployment of echo cancellers.
18
19
20
21
If digital telephones (i.e., conforming to ANSI/TIA-810-B) are used at each end of the
connection, and if the entire end-to-end connection is over a digital based network, then the loss
plan is very simple. The digital sets provide the desired overall loudness rating, hence the VG
would not insert any loss or gain in the voice channel.
22
23
24
In practice, however, many VG connections will involve the public network in one form or
another, either by connections to the public switched network or by connections to private
networks over public network facilities (e.g., tie trunks).
25
26
27
28
29
30
In general, connections through the public network can be analog either in whole or in part and
involve 2-to-4 wire conversions. The allocation of loss among the public network subsystems
affects the noise at the telephone receiver, the echo heard by the talker and the listener, the
probability of hearing other conversations, and the probability of causing interference on
connections being used by other customers. Also signals at too high a level can cause
intermodulation distortion in some older carrier systems.
31
32
33
34
35
This standard recommends a loss and level plan for VGs that specifies the amount of loss or gain
to be inserted by the gateway when interfacing with the various elements of public and private
telecommunications networks. It is intended to be coordinated with the public network loss plan
according to the fundamental loss planning principles of ANSI T1.508 and it is intended to fully
comply with ANSI/TIA-968-A and ANSI/TIA-968-A-1.
36
The loss and level plan consists of two parts:
37
38
39
40
41
42
43


A full-channel plan that defines the port-to-port losses for all connections types. This is
similar to the PBX loss level plan as specified in ANSI/TIA-464-C and ANSI/TIA-464-C-1,
and ensures satisfactory interworking with the existing TDM-based public and private
networks
A half-channel plan that defines the port-to-packet network and packet network-to-port
losses. This plan is specific to IP/packet telephony and will facilitate the interworking of
national and international IP/packet telephony networks.
13
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
6.2 Port-to-Port Loss Allocation
2
3
4
The allocation of the port-to-port loss to the send and receive ports directly influences the
available dynamic range of the PCM coding scheme. This may lead to substantial impacts on
speech transmission quality as perceived by the user.
5
6
Care should be taken to ensure that excessive input gain or loss does not cause either PCM
encoding overload, or a poor signal-to-noise ratio, at the 0 dBr point.
7
See Annex B.3 for further information on port-to-port loss allocation.
8
6.3 Digital Padding
9
10
11
12
Digital padding refers to the technique of implementing port-to-port losses by changing the level
of the digitally encoded voice. Digital padding should be avoided wherever possible, as it has the
potential to increase quantization distortion. Losses involving analog ports should be
implemented before encoding or after decoding.
13
6.4 Voice Gateway Loss Plan Assumptions
14
15
16
17
The port-to-port losses for VGs were developed based on the loss plans for public and private
networks. The VG loss plan is intended to provide satisfactory grade-of-service (GoS)
performance and compatibility with the public and private network loss plans. The following
assumptions were the prime considerations:
18
19
(1) The transmission loss and level plan of the PSTN, which is primarily an all-digital network
with some fixed loss as described in T1.508, forms a basis for the private network loss plan.
20
21
(2) Digital end offices insert 6 dB of loss, as described in T1.508, in the receive direction of
analog access lines to ensure network stability, echo control and optimum end-to-end levels.
22
(3) Transmission facilities have losses compatible with the VG port-to-port losses.
23
(4) The ONS connection loss from the station to the VG is typically low (0 dB assumed).
24
(5) The OPS connection loss from the station to the VG is typically significant (4 dB assumed).
25
26
(6) FXD connections require a loss equivalent to a typical analog connection to be inserted at
the VG, as the channel bank is located close to the DEO.
27
(7) Non-proprietary VG stations have the following loudness ratings:
28
Station
SLR (dB)
RLR (dB)
Notes
29
OPS
8
-3
a, b)
30
ONS
4
-7
a, c)
31
DGS
8
2
a, d)
32
Notes:
33
34
35
a) The OPS (off premise station) LRs are representative of 2500-type POTS sets operating
on 26 gauge/2.75 km loops with normal 48 volt battery feed and 600 ohm termination, as
measured at a VG OPS port. See ANSI/TIA-470.110-C, Annex E for further details.
36
37
38
b) The ONS (on premise station) LRs are representative of 2500-typePOTS sets operating
on very short loops with the typical current-limited battery feed and 600 ohm
termination of VG ONS ports. See ANSI/TIA-470.110-C, Annex E for further details.
39
40
41
c) The DGS (digital station) loudness ratings are chosen to improve interoperability with
the standard ITU LR levels for digital sets of SLR = 8 dB and RLR = 2 dB. See
ANSI/TIA-810-B for further details.
14
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
6.5 Full-Channel Loss and Level Plan Requirements
2
3
4
5
6
The intent of the full-channel loss plans specified in Table 1 and Table 2 shall be implemented in
Voice Gateways. The associated level plans are provide in Table 3 and Table 4. Related
regulatory information on allowable net amplification between ports is provided in Table 5. A
half-channel loss plan for packet-based voice services is provided in Table 6 that gives some
clarification of the intent of the full-channel loss plan.
7
6.5.1 Insertion Loss Criteria for Voice Gateways
8
9
10
11
12
Enterprise VGs normally have call-by-call adjustable loss plans that permit compliance with the
full matrix of port-to-port connections, as specified by the loss plan in Table 1. MTA and IAD
VGs usually have fixed loss plans. Table 2 is a fixed loss plan subset of Table 1 that is
appropriate for MTA and IAD VGs. The VG interfaces depicted in the loss plan are defined in
Figure 6, and described in Clause 4.6.
13
6.5.2 Port-to-Port Loss Table Interpretation
14
15
In Table 1 and Table 2, arrows at the row and column designators indicate the transmission
direction in which the co-ordinate loss values are to be inserted.
16
17
18
For example Table 1, co-ordinate 1B indicates a nominal port-to-port loss of 9 dB from the ONS
interface to the OPS interface, and co-ordinate 2A indicates a 9 dB loss in the other direction,
from the OPS interface to the ONS interface.
19
Note: This is a loss plan, therefore negative values denote gain; e.g., -6 indicates 6 dB of gain.
20
6.5.3 Port-to-Port Loudness Ratings Table Interpretation
21
22
23
24
Table 3 and Table 4 are provided to show the relationship between OLR and SLR, Loss, and
RLR. For example, for an ONS to OPS connection, the ONS SLR is 4 dB, the VG loss is 9 dB
(from 1B in Table 1), and the OPS RLR is -3 dB. The overall loudness ratings is therefore
4 + 9 - 3 = 10 dB. See Annex B.2 for further information on loudness ratings.
25
6.5.4 Voice Gateway Loss Ranges
26
27
28
The port-to-port losses in Table 1 and Table 2 are the recommended nominal values. Although
there are no mandatory loss ranges associated with these values, it is desirable that the average
1 kHz loss fall within 0.5 dB of the nominal loss values given in Table 1 and Table 2.
29
6.5.5 ANSI/TIA-968-A and ANSI/TIA-968-A-1 Requirements
30
31
32
33
34
35
36
ANSI/TIA-968-A-1, an addendum to ANSI/TIA-968-A, relaxes the encoded analog content
signal power limitations, relative to ANSI/TIA-968-A. The result is less allowable net
amplification between some ports, more allowable amplification between other ports and no
change in the allowable net amplification between most ports. The revised allowable Net
Amplification between ports requirements are specified in Table 4.6 of ANSI/TIA-968-A-1,
which for convenience, is reproduced in this standard as Table 5. Note that the values in Table 5
are in terms of gain, while the values in Table 1 and Table 2 are in terms of loss.
37
38
39
40
The requirements in Table 1 and Table 2 are coordinated with Table 4.6 of ANSI/TIA-968-A-1,
so that all the values specified in Table 1 and Table 2 have either the same loss or more loss than
Table 4.6 of ANSI/TIA-968-A-1. This means that compliance with Table 1 and Table 2 of this
standard guarantees compliance with Table 4.6 of ANSI/TIA-968-A-1.
41
42
43
44
45
46
The situation where the value of loss specified in Table 1 and Table 2 are identical to the value
of loss specified in Table 4.6 of ANSI/TIA-968-A-1 is addressed in Note 4 of Table 4.6. Note 4
permits the values in Table 4.6 to be exceeded as long as the absolute signal power limitations
for the port are not exceeded. This includes Clause 6.5.4 of this standard, which allows a
tolerance of up to 0.5 dB of additional gain, relative to the nominal losses specified in Table 1
and Table 2.
47
15
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Table 1 – Enterprise Voice Gateway Loss Plan
2
1
2
3
4
5
6
7
8
A
B
C
D
E
F
G
H
ONS
OPS
DGS
WAN
DAL
FXO
FXD
ATT








12
9
9
9
9
0
3
6
9
6
6
6
6
0
0
0
3
0
0
0
0
-62
-32
0
3
0
0
0
0
-62
-32
0
3
0
0
0
0
-62
-32
0
3
0
0
0
0
0
0
0
6
0
3
3
3
0
0
0
9
3
3
3
3
0
0
0
Loss1 (dB)
ONS 

OPS

DGS
WAN 
DAL 
FXO 
FXD 

ATT
3
4
5
6
7
8
9
10
11
12
Note 1: Losses have been selected as multiples of 3 dB, assuming that this simplifies the
implementation.
Note 2: There is a potential risk of DTMF overload if an FXO analog trunk is connected to DGS,
WAN or DAL and the VG is located less than 2 km from the DEO due to the gain added
in the A/D direction. In these cases it is recommended that the FXD to DGS, WAN or
DAL setting be used instead because the FXD setting introduces 3 dB less gain in one
direction and 3 dB more loss in the other direction. See Annex B.4 ‘DTMF Overload on
Analog Trunks’.
13
Table 2 – MTA/IAD Voice Gateway Loss Plan
1
2
3
4
14
15
16
17
18
Loss1 (dB)
ONS 

DGS

PAL
DAL 
A
B
C
D
ONS
DGS
PAL
DAL




12
9
9
9
3
0
0
0
3
0
0
0
3
0
0
0
Note 1: Losses have been selected as multiples of 3 dB, assuming that this simplifies the
implementation. For the optimum OLR of 10 dB, the “to ONS” loss value is actually
13 dB.
16
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Table 3 – Enterprise Voice Gateway Loudness Ratings
2
ONS
OPS
DGS
WAN
DAL
FXO1
FXD1
ATT2
(dB)
SLR
4
8
8
8
8
17
14
15
RLR
OLR








OPS
-3
DGS
2
WAN
2
DAL
2








9
10
10
10
10
10
10
14
10
11
11
11
11
14
11
12
9
10
10
10
10
13
13
17
9
10
10
10
10
13
13
17
9
10
10
10
10
13
13
17
13
14
14
14
14
23
20
21
13
11
14
14
14
20
17
18
14
12
12
12
12
18
15
16
ONS1
-7
FXO1
6
FXD1
3
ATT2
1
3
4
Note 1: The loudness ratings for the FXO and FXD ports include a nominal 6 dB DEO loss.
5
6
Note 2: The loudness ratings for the ATT port include a nominal 2 dB trunk loss, see
Annex B.2.4, ‘ATT Network Interface Loudness Ratings’.
7
8
9
Table 4 – MTA/IAD Voice Gateway Loudness Ratings
ONS
DGS
PAL
DAL
1
(dB)
SLR
4
8
8
8
RLR
OLR




ONS1
-7
DGS
2
PAL
2
DAL
2




9
10
10
10
9
10
10
10
9
10
10
10
9
10
10
10
10
11
17
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
2
Table 5 – ANSI/TIA-968-A-1, Clause 4.5.2.5 - Allowable Net Amplification Between Ports
To →
From
↓
TIA-912-A
Port
Designations
ATT
N/A
DAL
DAL
DGS
ONS
OPS
FXO &
FXD
DAL
Lossless Tie
Trunk Port
(2/4 wire)
Sub-rate
1.544 Mbps
Satellite Tie
Trunk
Port (4-wire)
Sub-rate
1.544 Mbps
Tandem Tie
Trunk
Port (4-wire)
Integrated
Services
Trunk Ports
Approved
Digital TE
On Premises
Station Port
with
Approved TE
Off Premises
Station Port
(2-wire)
Analog Public
Switched
Network Ports
(2-wire)
Sub-rate
1.544 Mbps
Digital PBXCO Trunk
Ports (4-wire)
Tie Trunk Type Ports
Lossless
(2/4
wire)
Sub-rate
1.544
Mbps
Satellite
(4-wire)
Sub-rate
1.544
Mbps
Tandem
(4-wire)
Integrated
Services
Trunk
Ports
Off
Premises
Station
Ports
(2-wire)
ATT
N/A
DAL
DAL
OPS
0 dB
2 dB
2 dB
2 dB
2 dB
3 dB
3 dB
3 dB
1 dB
Analog
Public
Switched
Network
Ports
(2-wire)
Sub-rate
1.544
Mbps
Digital
PBX-CO
Trunk
Ports
(4-wire)
FXO &
FXD
DAL
-2 dB
0 dB
0 dB
0 dB
0 dB
-2 dB
0 dB
0 dB
0 dB
0 dB
-2 dB
0 dB
0 dB
0 dB
0 dB
0 dB
0 dB
-2 dB
0 dB
0 dB
0 dB
0 dB
0 dB
0 dB
2 dB
4 dB
4 dB
4 dB
4 dB
4 dB
4 dB
3 dB
3 dB
0 dB
3
4
Note 1: In this table, positive values denote gain and negative (-) denotes loss
5
6
7
Note 2: The ANIS/TIA-968-A-1 limits shown in Table 5 are only provided as a convenience to
users of this standard. The user should consult the latest revision of the ANSI/TIA-968-A
standard and/or addendums to ensure compliance.
8
18
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
6.6 Half-Channel Loss and Level Plan
2
6.6.1 Overview
3
4
5
6
Developing a loss plan is generally a complex process, as the objective is to ensure a satisfactory
overall loudness rating (OLR) for all connections types. To do this the loudness ratings of the
end points (telephones), and the transmission loss between the end points, must be known for
each connection type.
7
8
9
10
11
This is a trivial exercise in a purely packet telephony environment, if one assumes that the end
points are digital telephones with an LR of 8 dB and 2 dB (in line with ITU-T
Recommendations), and that no gains or losses are introduced in the digital transmission path. In
this case the OLR for any digital telephone-to-telephone connection world-wide is the ITU-T
Recommendation G.101 objective of 10 dB.
12
13
14
The complexity is introduced when the packet telephony network connects to analog telephones
and trunks. In this case the LRs of the telephones and trunks vary, although a loss-less digital
transmission path can be maintained.
15
16
17
A half-channel loss plan for national and international packet telephony networks can be
implemented based on the premise that only the LRs vary, and that the packet network does not
introduce any additional gain or loss.
18
19
20
21
Full-channel loss plans are still required for VGs, as VGs can also connect to existing analog and
TDM based digital networks. These connections require losses to be defined on a port-to-port
basis for technical and regulatory reasons. A half-channel loss plan can therefore be considered
as a sub-set of a full-channel loss plan that is only applicable to packet network connections.
22
6.6.2 Concept
23
24
25
26
27
The basic concept in the half-channel loss plan is to adjust all send levels on a packet telephony
network to the optimum SLRHC of 8 dB. Digital telephones provide the reference SLR of 8 dB by
definition. This is not an original concept, as it is the basis of the European dBr reference system.
The move to standardize the North American digital telephone LRs to the ITU-T recommended
levels makes this practical for packet telephony networks.
28
29
The same basic concept could be applied to the current non-packet PSTN and private networks,
but existing industry standards and may make it difficult to implement.
30
6.6.3 Principle of Operation
31
32
33

The originating entity will adjust the SLR of the sending port to 8 dB at the ingress to the
packet network, i.e., the 0 dBr point. The SLR at the 0 dBr point is defined as the SLRHC
(Half-Channel SLR).
34
35
36

The terminating entity will adjust the RLR of the receiving port to 2 dB at the egress from
the packet network, i.e., the 0 dBr point, to achieve the optimum OLR of 10 dB at the
receiving port. The RLR at the 0 dBr point is defined as the RLRHC (Half-Channel RLR).
37
38
39
Note: The internationally recognized optimum OLR is 10 dB. See ITU-T Rec. G.101.
The advantage of this approach is that neither entity requires knowledge of the other, so loss
planning becomes a local issue.
40
19
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
Applicability
1
6.6.4
2
3
This loss plan applies to all kind of packet-based voice services, irrespective whether they
provide:
4

real time conversational telecommunication between human subjects, or
5
6

listening-only telecommunication from a machine interface (stored speech) to a human
subject, or
7

speaking-only telecommunication from a human subject to a machine interface;
8
9
The half-channel loss plan only applies to connections routed via packet networks, other VG
port-to-port connections are subject to the full-channel loss plan recommendations.
10
6.6.5 Recommended Loss Ranges
11
The transmit and receive losses in Table 6 are the recommended nominal values.
12
13
Although there are no mandatory loss ranges associated with these values, it is desirable that the
average 1 kHz loss fall within 0.5 dB of the nominal loss values given in Table 6.
14
6.6.6 Packet Network Losses
15
16
17
It is critical for the operation of a half-channel loss plan that no gain or loss is inserted during
transmission through the packet network. Any level changes due to transcoding for example,
should be less than 1 dB.
18
19
Note: Transcoding refers to the conversion from one voice coding algorithm to another, e.g.,
G.726 to G.729.
20
20
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
6.6.7 Half-Channel Loss Plan Table
2
3
Table 6 shows the North American VG half-channel loss plan, given in loudness ratings and
respective loss.
4
Table 6 - Voice Gateway Half-Channel Loss Plan
WAN/PAL
0 dBr Point

(dB)
ONS
OPS
DGS
WAN
PAL
DAL
FXO
FXD
ATT
a
b
SLR
Tx
Loss1
3
0
0
0
0
0
-6
-3
0
4
8
8
8
8
8
17
14
15
c
=(a + b)
SLRHC
d
=(e + f)
RLRHC
7
8
8
8
8
8
112
112
15
2
3
2
2
2
2
6
6
4
e
f
Rx
Loss1
9
6
0
0
0
0
0
3
3
RLR
g
=(c + d)
OLR3
-7
-3
2
2
2
2
6
3
1
9
11
10
10
10
10
17
17
19
h
=(8 + d)
Desirable
OLR
10
11
10
10
10
10
14
14
12
5
6
7
Column a shows the SLR of the telephone and trunk between the acoustic interface and the
connection point to the VG.
8
9
Column b shows the transmit loss required to achieve the required SLRHC at the 0 dBr point,
except for the analog trunks which use the historical send loss.
10
Column c shows the resulting Half-Channel SLR (SLRHC) at the 0 dBr point (WAN/PAL).
11
Column d shows the resulting Half-Channel RLR (RLRHC) at the 0 dBr point (WAN/PAL)..
12
13
14
Column e shows the receive loss required to achieve the desirable OLR, based on the RLR
shown in column f, and the optimum SLR of 8 dB, except for the analog trunks which
use the historical receive loss.
15
16
Column f shows the RLR of the telephone and trunk between the acoustic interface and the
connection point to the VG.
17
Column g shows the resulting OLR, based on the actual SLR.
18
Column h shows the desirable OLR, based on the optimum SLR of 8 dB.
19
Notes:
20
21
1. Losses have been selected as multiples of 3 dB, assuming that this simplifies the
implementation. All numbers in Table 6 are in dB.
22
23
24
2. It is not possible to achieve the optimum SLRHC of 8 dB for connections from analog
networks due to the potential for DTMF signaling overload. See Annex B.4 ‘DTMF Overload
on Analog Trunks’.
25
26
3. The OLR values shown in the table are as perceived by the listener, i.e. this is shown as a
one-way connection.
21
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
6.6.8 Network Stability
2
3
There is a potential for instability in connections involving 2-to-4 wire conversions if the open
loop gain of the 4-wire loop approaches 0 dB.
4
5
6
Additional losses are inserted in public and private analog and digital TDM-based networks to
ensure they are unconditionally stable, and the resultant high OLRs are accepted for mixed 2wire and 4-wire networks.
7
8
9
10
11
The use of this approach for a half-channel plan would result in unacceptable OLRs for some
connection types. Fortunately, the requirement for unconditional stability is not required in
packet-based networks as a digital 4-wire loop will only oscillate when the hybrids at both ends
of the loop are un-terminated, and under these conditions the 4-wire loop would not be connected
to any analog loops that could be affected by digital loop oscillation.
12
Notes:
13
14
15
1. Oscillation in a 4-wire loop has shown to cause harm to analog frequency division
multiplexing (FDM) transmission systems by affecting the FDM equipment's signal level
management. There is no potential for such harm in purely digital systems.
16
2. See Annex B.5 for further information on open loop loss and network stability.
17
6.6.8.1 Stability Loss
18
19
20
21
22
23
24
ITU-T Recommendation G.122 specifies the minimum stability loss for national systems
required to prevent instability on international calls. The stability loss of each national system
represents one half of the open loop loss (OLL) of the 4-wire loops required to establish an
international connection. This is equivalent to the VG loss on either side of a packet network
connection. A stability loss of 6 dB at all frequencies between 200 and 3600 Hz will ensure that
the G.122 requirements are met. However, stability losses of between 6 dB and 0 dB will
formally comply with the present requirements of G.122.
25
26
This need not be a requirement for purely packet-based connections for the reasons discussed
above.
27
22
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
7
Loss Parameters
2
7.1 Frequency Response
3
4
5
6
The frequency response recommendations for the A/D and D/A conversions are shown in
numerical form in Table 7, and graphically in Figure 7 & Figure 8 and Figure 9 & Figure 10,
respectively. These figures are illustrative only. Measurement results must be normalized to 0 dB
at 1004 Hz.
7
Table 7 - Frequency Response Recommendations
Analog to Digital
Digital to Analog
Loss (dB)
Loss (dB)
Frequency
(Hz)
Min
Max
Min
Max
200
0
3
0
2
300
-0.25
0.5
-0.25
0.5
3000
-0.25
0.5
-0.25
0.5
3200
-0.25
0.75
-0.25
0.75
3400
0
1.5
0
1.5
3400 to 4000
-14x+14
-
-14x+14
-
4000 to 4600
-18x+14
-
-14x+14
-
4600 to 12000
32
-
28
-
8
Where: x  sin   4000  F / 1200
9
10
Note: Positive numbers indicate higher loss and negative numbers indicate lower loss than the
reference loss at 1004 Hz.
11
7.1.1 Rejection of Power Line Interference
12
Rejection of power line interference should be greater than 20 dB at 60 Hz in the A/D direction.
13
7.2 Tracking Error and Overload Compression
14
7.2.1 Tracking Error
15
The tracking error for A/D and D/A conversions should not exceed the limits shown in Table 8.
16
17
The tracking error for all port-to-port connections should not exceed the limits shown in
Figure 11.
18
Table 8 - Voice Gateway Tracking Error Limits
Input Signal
Tracking Error (dB)
Level Range
(dBm)
Maximum
Average
0 to -37
±0.25
±0.125
-37 to -50
±0.5
±0.25
19
23
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Figure 7 - Voice Gateway Frequency Response - Analog to Digital
-5
Unacceptable Region
Loss (dB) relative 0 dB @ 1004 Hz m.
0
Acceptable Region
0 dB, 1004 Hz
5
Unacceptable Region
10
15
20
25
30
35
100
200
3400
1000
Frequency (Hz)
10000
A/D
2
3
4
Figure 8 - VG Frequency Response - Analog to Digital - In -1 to +4 dB Region Only
-1
Loss (dB) relative to 0 dB @ 1004 Hz m.
Unacceptable Region
0
Acceptable Region
1
0 dB, 1004 Hz
Unacceptable Region
2
3
4
100
200
1000
Frequency (Hz)
5
6
24
3400
10000
A/D
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Figure 9 - Voice Gateway Frequency Response - Digital to Analog
-5
Unacceptable Region
Loss (dB) relative 0 dB @ 1004 Hz m.
0
Acceptable Region
0 dB, 1004 Hz
5
Unacceptable Region
10
15
20
25
30
35
100
200
3400
1000
Frequency (Hz)
10000
D/A
2
3
4
Figure 10 - VG Frequency Response - Digital to Analog - In -1 to +4 dB Region Only
-1
Loss (dB) relative to 0 dB @ 1004 Hz m.
Unacceptable Region
0
Acceptable Region
1
0 dB, 1004 Hz
Unacceptable Region
2
3
4
100
200
1000
Frequency (Hz)
5
6
25
3400
10000
D/A
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
2
7.2.2 Overload Compression
3
4
For all port-to-port connections, the compression of a 1004 Hz input signal relative to a 1004 Hz,
0 dBm input signal should not exceed the values shown in Figure 11.
5
6
7
Note: Care should be taken to ensure that port-to-port losses are not implemented in a manner
that causes PCM encoding overload. See Annex B.3 for further information on port-to-port loss
allocation.
8
9
Figure 11 - Tracking Error and Overload Compression
10
11
26
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
8
Echo Control and Return Loss
2
3
4
Echo in transmission systems is due to reflections from impedance mismatches, and the most
common source of impedance mismatches in telephone networks is in the 2-to-4 wire converter
or hybrid. The echo return loss is defined for two directions:
5

4-wire to 4-wire, which is a function of the hybrid balance;
6

2-wire, which is a function of the 2-wire input impedance.
7
Active echo control using echo cancellers or suppressers is beyond the scope of this section.
8
8.1 Hybrid Balance Requirements
9
10
11
12
For each interface, the line or trunk side 2-wire analog port should be terminated with the
appropriate reference impedance (see 8.1.1.1). The reference impedances should consist of
passive elements. The hybrid balance, when measured as described in Annex A.5, should exceed
the values in Table 9 on 95 percent of the interfaces.
13
Note: Two-wire analog trunks include FXO, DID, and ATT ports.
14
15
16
17
Table 9 - Voice Gateway Minimum Hybrid Balance Recommendations
Frequency Band
Hybrid Balance
200 to 500 Hz
Equal to or greater than the values located on a straight line intersecting
17 dB at 200 Hz and 22 dB at 500 Hz.
500 Hz to 2.5 kHz
22 dB
2.4 kHz to 3.4 kHz
Equal to or greater than the values located on a straight line intersecting
22 dB at 2.5 kHz and 17 dB at 3.4 kHz.
Note: All points are plotted on a log/linear scale with the impedance values in dB on the linear
axis and the frequency in Hz on the logarithmic axis.
18
19
8.1.1.1 Hybrid Balance Reference Impedances
20
8.1.1.1.1
21
22
23
A reference impedance of 600  is recommended for ONS ports. This network has been selected
to match the distribution of telephone set impedances expected in the VG on-premises
environment.
24
8.1.1.1.2
25
26
A reference impedance of 600  is recommended for OPS and two-wire trunk ports that connect
to facilities with line treatment2.
27
8.1.1.1.3
28
29
The reference impedance shown in Figure 12 is recommended for OPS and two-wire trunk ports
that connect to facilities without line treatment. This impedance has been found to provide the
ONS Ports
OPS and Two-Wire Analog Trunk Ports With Line Treatment
OPS and Two-Wire Analog Trunk Ports Without Line Treatment
2 As used in this context, the term "line treatment" means any equipment (e.g., an impedance compensator,
a repeater, or a range extender) that presents a nominal impedance of 600  at the interface connecting to
the port.
27
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
2
best single compromise to the distribution of OPS line and 2-wire trunk impedances expected in
the North American telephone network.
3
4
Figure 12 - OPS/2-Wire Trunk Reference Impedance
1000 
350 
0.21 F
5
6
7
8.2 Input Impedance Requirements
8
9
10
11
12
13
14
Requirements are given only for paths through the switch for which the connecting port interface
(the interface on the other side of the switch) is 4-wire. In this way, the measured results are
independent of any feedback resulting from imperfect balance of the far-end hybrids on 2-wire
interfaces. While such imperfect balance does influence the 2-wire interface input impedance and
the loss of the switch when it connects two 2-wire lines, the effects on in-service performance are
controlled by having separate requirements for hybrid balance (Clause 8.1) and insertion loss
(Clause 6).
15
16
17
18
The requirements for the input impedance are given in terms of a reference impedance (Z R) and
minimum return loss. The return loss is defined in Annex C where the input impedance is
denoted by ZI and reference impedance by ZR. The return loss is a function of frequency, and
increases without limit as the input impedance approaches the reference impedance.
19
20
21
For each 2-wire and 4-wire analog port, the input impedance (Input Z) in terms of return loss
(single frequency return loss and echo return loss) should exceed the values in Table 10 or
Table 11 on 95 percent of the interfaces, when measured as described in Annex A.6.
22
8.2.1.1 Input Impedance Reference Impedances
23
8.2.1.1.1
24
25
26
ONS ports should meet the minimum input impedance requirement when using a reference
impedance consisting of either 600  or a complex reference impedance as described in
8.2.1.1.4.
27
8.2.1.1.2
28
29
30
OPS ports should meet the minimum input impedance requirement with a reference impedance of
600  and may, optionally, also meet the input impedance requirement with a complex reference
impedance as described in 8.2.1.1.4.
31
8.2.1.1.3
32
33
Two-wire analog trunks ports should meet the minimum input impedance requirement with a
reference impedance of 600 .
34
Note: Two-wire analog trunks include FXO, DID, and ATT ports.
ONS Ports
OPS Ports
Two-Wire Analog Trunk Ports
35
28
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
2
8.2.1.1.4
Complex Reference Impedances
3
4
5
This option allows flexibility in the design of line input impedance for specific applications or
terminations. The recommended reference impedance for measuring the return loss of lines
designed with a complex input impedance network is either:
6

The network shown in Figure 12,
7
8

A network consisting of a 275  resistor in series with a parallel circuit of a 780 
resistor and 0.15 µF capacitor, or
9

A network consisting of a 600  resistance in series with a 2.16 µF capacitor.
10
11
Table 10 - Voice Gateway Return Loss Recommendations for 600  ZR
Return Loss
Frequency Band
Minimum
Desirable
200 to 500 Hz
Equal to or greater than the values
located on a straight line intersecting
14 dB at 200 Hz and 22 dB at 500 Hz.
Equal to or greater than the values
located on a straight line intersecting
14 dB at 200 Hz and 26 dB at 500 Hz.
500 Hz to 2.5 kHz
22 dB
26 dB
2.4 kHz to 3.4 kHz
Equal to or greater than the values
located on a straight line intersecting
22 dB at 2.5 kHz and 14 dB at 3.4 kHz.
Equal to or greater than the values
located on a straight line intersecting
26 dB at 2.5 kHz and 14 dB at 3.4 kHz.
12
13
Table 11 - Voice Gateway Return Loss Recommendations for Complex ZR
Return Loss
Frequency Band
Minimum
Desirable
200 to 500 Hz
Equal to or greater than the values
located on a straight line intersecting
14 dB at 200 Hz and 22 dB at 500 Hz.
-
500 Hz to 2.5 kHz
22 dB
-
2.4 kHz to 3.4 kHz
Equal to or greater than the values
located on a straight line intersecting
22 dB at 2.5 kHz and 14 dB at 3.4 kHz.
-
14
15
16
Note: All points are plotted on a log/linear scale with the impedance values in dB on the linear
axis and the frequency in Hz on the logarithmic axis.
29
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
9
Noise and Distortion Impairments
2
9.1 Idle-Channel Noise
3
4
Idle-channel noise is the short-term, average, absolute noise power measured with a flat or Cmessage weighting in the absence of signal.
5
6
Compliance with the idle-channel noise requirements should be determined as described in
Annex A.7.
7
9.1.1 3 kHz Flat Noise
8
9
(1) The 3 kHz flat weighted noise should not exceed 35 dBrn on 50 percent of the
connections.
10
11
(2) The 3 kHz flat weighted noise should not exceed 39 dBrn on 95 percent of the
connections.
12
13
14
For interface transmission levels other than 0 dB, the 3 kHz flat weighted noise requirement
should be shifted by a value that corresponds to the difference between the transmission level at
that interface and 0 dB.
15
9.1.2 C- Message Weighted Noise
16
17
18
The maximum (95 percent) C-message weighted absolute noise power at an interface should not
exceed the values given in Table 12. It is desirable that the mean C-message weighted absolute
noise power also comply with the values shown in the table.
19
20
21
For interface transmission levels other than 0 dB, the C-message weighted noise requirement
should be shifted by a value that corresponds to the difference between the transmission level at
that interface and 0 dB.
22
Table 12 - Voice Gateway C-Message Weighted Noise Requirements
C-Message Weighted Noise (dBrnC)
in the Absence of Signal
Connection Type
Mean
(Desirable)
95%
(Maximum)
Analog-to-analog
16
20
Analog-to-digital
15
19
Digital-to-analog
9
13
23
24
30
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
9.2 Longitudinal Balance
2
3
The VG interfaces that are subject to longitudinal balance requirements include loop/ground start
DEO/FXO trunks, reverse battery (DID) trunks, OPS lines, and digital service trunks.
4
9.2.1
5
(1)
6
The longitudinal-to-metallic balance is defined as:
Longitudinal-to-Metallic Balance
Definition.
7
Longitudinal Balance (dB) = 20 log|Vs / Vm|.
8
9
where Vs is the disturbing longitudinal rms voltage, and Vm the resulting metallic rms voltage of
the same frequency.
10
11
The longitudinal-to-metallic balance recommendations only apply to analog ports. A low
conversion of longitudinal into metallic noise is required to limit noise on the talking circuit.
12
(2)
13
14
15
The longitudinal-to-metallic balance of analog ports, when measured as described in Annex
A.8.1, should meet or exceed the criteria of Table 13. It is desirable that the average balance be
within the region labeled "desirable" in Figure 13.
16
Table 13 - Voice Gateway Longitudinal-to-Metallic Balance Requirements
Recommendations.
Frequency (Hz)
Minimum Balance
(dB)
Average Balance
(dB)
200
58
63
500
58
63
1 kHz
58
63
3 kHz
53
58
17
18
Figure 13 - Longitudinal Balance Limits
90
(60,80)
80
Des irable Reg ion
(200,77.4)
(600,70)
70
(1000,68.1)
Accep tab le Regio n
Balance
(dB)
(200,58)
60
Unacceptable Regio n
50
500
Frequ en cy (Hz)
50
19
31
(3000,58.7)
(1000,58)
(3000,53)
(4000,54)
5000
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
9.2.2 Metallic-to-Longitudinal (Transverse Balance) Balance
2
9.2.2.1 Definition
3
The transverse balance is defined as:
4
Transverse Balance (dB) = 20 log |Vm / Vs|
5
6
where Vs is the longitudinal rms voltage produced across a longitudinal termination Z1, and Vm
is the metallic rms voltage across the tip-and-ring interface terminals of the VG.
7
8
9
Transverse balance (metallic-to-longitudinal balance) is specified in ANSI/TIA-968-A to ensure
that a metallic signal is not converted into a longitudinal signal that could cause excessive noise
in other pairs of a multi-pair cable.
10
9.2.2.2 Requirements.
11
12
13
The VG should meet the minimum transverse balance requirements as given in
Table 14 for analog interfaces and Table 15 for digital service interfaces, when measured as
described in Annex A.8.2.
14
(1)
15
16
The criteria given in Table 14 should be met for all possible combinations of through
transmission paths between analog DEO trunk and station line interfaces of the VG.
17
Table 14 - Transverse Balance Requirements for Analog Interfaces
Analog Interfaces
Interface
State
Frequency Range
Minimum Balance (dB)
200 Hz to 1 kHz
60
1 kHz to 4 kHz
40
Off-hook
200 Hz to 4 kHz
40
DEO Trunk-Ground Start
Off-hook
200 Hz to 4 kHz
40
Reverse Battery (DID)
Off-hook
200 Hz to 4 kHz
40
OPS Line
Off-hook
200 Hz to 4 kHz
40
DEO Trunk-Loop Start
On-hook
18
19
20
(2)
Digital Interfaces
Table 15 - Transverse Balance Requirements for Digital Interfaces
Interface
1.544 Mbps Digital Trunk
Frequency Range
15 kHz to 1.544 MHz
21
22
32
Minimum Balance (dB)
36
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
2
9.3 Crosstalk
3
9.3.1 Requirement
4
5
The crosstalk coupling loss for every port-to-port connection, over the 200 to 3400 Hz frequency
band, should comply with the following criteria:
6
7
8
(1)
The crosstalk coupling loss between any established connection through the VG and at
least 95 percent of all other through connections should be at least 75 dB, and it is
desirable that this loss be at least 80 dB.
9
10
(2)
The crosstalk coupling loss between any established connection through the VG and any
other through connection should be at least 70 dB.
11
12
Compliance with the crosstalk coupling loss recommendations should be determined as described
in Annex A.9.
13
9.4 Quantization Distortion
14
15
16
Ninety-five percent or more of all A/D and D/A connections should comply with the
recommendations in Table 16, where the input signal is a 1004 Hz sinewave and the output
distortion is measured using C-message weighting.
17
Table 16 - Voice Gateway Quantization Distortion Requirements
Input Signal
Level (dBm)
Input/Output Level Ratio
(dB)
0 to -30
35
-40
29
-45
25
18
19
9.5
Single-Frequency Distortion
20
21
Ninety-five percent or more of all A/D and D/A connections in each connection category should
comply with the following distortion limit:
22
23
24

For input signals at a constant 0 dBm level and any single frequency in the range of 0 to 12
kHz, the corresponding output signal power level at any other single frequency should not
exceed -28 dBm.3
3
The -28 dBm limit is dependent upon the characteristics of the transmit and receive filters of the Voice
Gateway. In the 0 to 3400 Hz frequency range, the limit value is influenced by the characteristics of the
receive filter; in the 3.4 to 4.6 kHz range the limit value is dependent upon both transmit and receive
filters; and in the 4.6 to 12 kHz range, the limit value is dependent upon the characteristics of the
transmit filter and should be -32 dBm.
33
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
10 Other Impairments
2
3
4
5
The following requirements apply to VGs intended to pass voiceband data. The following
requirements are given, in addition to the voice requirements, to verify that the VG will function
in a manner that will not be seen as an impairment to the performance of voiceband data
modems.
6
10.1 Intermodulation Distortion
7
8
9
Intermodulation or harmonic distortion is caused by nonlinearities present in the electric-toelectric transfer function of the VG. This form of distortion is of primary concern to the
transmission of data.
10
11
12
Intermodulation distortion is measured using the four-tone method that employs two pairs of
equal-level tones transmitted at a total, composite power level of -13 dBm. One pair consists of
the frequencies 857 and 863 Hz; the second pair uses the frequencies 1372 and 1388 Hz.
13
14
15
16
17
Intermodulation distortion is measured as the second- and third-order products resulting from the
application of the four tones. The second- and third-order products are denoted as R2 and R3,
respectively. R2 is the average power level in the 503-to-537 Hz and 2223-to-2257 Hz frequency
bands, expressed in dB below the received power level. R3 is the total power level in the 1877to-1923 Hz frequency band, expressed in dB below the received power level.
18
19
20
21
At input port signal power levels other than 0 dBm, the four-tone signal power levels should be
shifted by a value that corresponds to the difference between the signal level at the interface and
0 dBm. Since the R2 and R3 products are expressed in dB below the received signal level, their
values are not affected by non-zero reference signal levels.
22
23
The intermodulation distortion limits on 95 percent or more of all connections should meet or
exceed the values given in Table 17.
24
Table 17 - Intermodulation Distortion Limits for Voice Gateways
Distortion Limits
(dB below received level)
R2
R3
46 dB
56 dB
25
26
34
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
10.2 Envelope Delay
2
10.2.1 Definitions
3
4
5
6
7
Envelope Delay (ED) of a system is the propagation time through the system of a low-frequency
sinusoidal envelope of an amplitude modulated sinusoidal carrier. If the frequency range of
interest is denoted by R4, the carrier frequency is varied throughout R to obtain the ED as a
function of frequency. The carrier is 50 percent amplitude-modulated with a sinusoidal signal of
frequency 83.3 Hz.
8
9
Relative Envelope Delay (RED) is the difference between the ED at a given frequency f and the
global minimum ED within the range R.
10
10.2.2 Relative Envelope Delay (RED) Requirements
11
(1)
12
On 95 percent of the connections of this type
Station Interface-to-Trunk Interface and Trunk Interface-to-Trunk Interface
13
14

in the frequency range from 800 through 2700 Hz, the RED curve should lie below curve A
in Figure 14;
15
16

it is desirable that in the frequency range from 500 through 3000 Hz, the RED curve lie
below curve B in Figure 14.
17
(2)
18
19
20
21
22
The requirements for this connection allow twice the RED of those in 10.2.2(1). More precisely,
let A' be a curve obtained by multiplying by 2 each ordinate of the curve A in Figure 14 and let
B' be a curve obtained by multiplying by 2 each ordinate of the curve B in Figure 14. Then the
RED requirements for connections of this type are obtained from those in 10.2.2(1) by
substituting A' for A and B' for B.
4
Station Interface-to-Station Interface
A general symbol R is used here because the frequency range of interest may change with application.
For example, for mandatory requirements of this section R = [800 Hz, 2700 Hz], while for objective
requirements R = [500 Hz, 3000 Hz].
35
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Figure 14 - Relative Envelope Delay vs. Frequency
2
3
36
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
10.3 Impulse Noise
2
3
The following impulse noise limits should be met under fully loaded busy-hour VG traffic
conditions.
4
5
6
(1)
On 95 percent or more of all connections through each connection category, the impulse
noise level should not exceed zero counts above 55 dBrnC over a measurement interval of
five minutes.
7
8
(2)
It is desirable that the impulse noise level does not exceed zero counts above 47 dBrnC
over a measurement interval of five minutes.
9
10.4 Jitter
10
11
Jitter on a port-to-port connection should not exceed 2 degrees within the 4-to-300 Hz frequency
band.
12
10.5 Gain Hit
13
14
15
16
There should be no more than one gain hit per hour at a threshold level of 3 dB. If there is more
than one hit in a period of 1 hour, the subsequent hour should have zero hits. A gain hit is an
incidental modulation resulting in a rapid positive or negative shift of signal gain lasting for a
period of at least 4 ms.
17
10.6 Phase Hit
18
19
20
21
There should be no more than one phase hit per hour exceeding a threshold of 20 degrees. If
there is more than one phase hit in a period of 1 hour, the subsequent hour should have zero hits.
A phase hit is an incidental modulation resulting in a rapid positive or negative shift of signal
phase lasting for a period of at least 4 ms.
22
10.7 Dropout
23
24
25
There should be no more than one dropout per hour exceeding a threshold of 6 dB. If there is
more than one dropout in a period of 1 hour, the subsequent hour should have zero dropouts. A
dropout is a negative gain hit lasting a period of at least 10 ms.
26
10.8 Peak-to-Average Power Ratio
27
28
The VG should pass a signal, analog port-to-analog port, with a peak-to-average power ratio
(P/AR) of 95.
29
30
P/AR = 100 x ((2Ep/EFWA)-1), where Ep is the normalized peak and EFWA is the normalized
full rectified average of the envelope.
37
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
11 Signal Levels
2
3
The VG should comply with ANSI/TIA-968-A and/or ANSI/TIA-968-A-1, Clause 4.5, for the
following signal level limitations:
4
5
6
7
8
9
10
(1)
In-band Signal Power Limits
(a) Internal Signal Sources Not Intended for Network Control Signaling
(b) Internal Signal Sources Intended Primarily for Network Control Signaling
(c) Through Transmission
(d) Idle State Circuit Stability for Tie Trunks
(e) Metallic Signal Power at Frequencies in the range 3995 to 4005 Hz
(f) Longitudinal Voltage in the 100- to 4000 Hz Frequency Range.
11
12
13
14
15
(2)
Out-of-Band Signal Voltage Limits
(a) Metallic Voltage
(b) Longitudinal Voltage.
16
17
18
19
20
21
22
23
The above listed signal limitations should apply to:
(1)
(2)
(3)
(4)
(5)
(6)
Analog Trunk interfaces (ground start, loop start, DID)
OPS Lines
Analog Tie Trunks
Digital Trunk interface (ground start, loop start, DID, ISDN Basic Rate and Primary
Rate) with encoded analog contents
Digital OPS Lines with encoded analog contents
Digital Tie Trunk interface with encoded analog contents.
38
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Annex A (informative) - Measurement Guidelines
2
This annex is informative only and is not part of this standard.
3
A.1 Gain Ripples in the Measurement Path
4
5
6
7
8
In any digital VG, connections from a 2-wire analog port to a 2-wire analog port will constitute a
closed-loop feedback system. The feedback signal will cause ripples in the net through-gain
response of a 2-wire to 2-wire connection. If care is not exercised, the ripple effect will influence
measurement accuracy. The following two techniques for avoiding ripple influence on
measurements are suggested:
9
10
11
12
(1)
Perform test measurements on a 2-wire to 4-wire basis. This approach eliminates the
feedback signal. Where appropriate, the requirements contained in these sections have been
divided into transmit and receive portions to facilitate this approach. It will be necessary to
employ a digital test meter and designated digital test sequences for these types of measurements.
13
14
Alternatively, a half-channel test, in which the two directions of transmission are terminated
within the switching fabric, may be used (see Clause 8).
15
16
17
18
19
(2)
Maintain a high-quality impedance match at each 2-wire to 4-wire interface to minimize
the feedback signal. This approach requires use of a test impedance that closely matches the
hybrid balance impedance. To satisfactorily reduce the ripple caused by the feedback signal, a
hybrid balance of 25 dB (or greater) should be maintained at each 2-wire to 4-wire interface in
the test connection.
20
A.2 Transmission Level Translation
21
22
Each the requirement in this section has been written with respect to the 0 dBr point in the
switch. A 0 dBm0 signal at this point will decode to 0 dBm, or 1 mW in 600 .
23
24
25
In many cases, the interface level will be different from the 0 dBr point due to the losses
introduced to meet the loss plan. In these cases (unless otherwise stated) the appropriate interface
loss should be included when determining compliance with the requirements.
26
27
See Annex B.6 for further information on 0 dBr points, the definition of 0 dBm0, and
transmission level translation.
28
29
30
31
32
33
34
35
36
37
A.3 Dial-up Port for Trunk Testing
To avoid the gain variations that can occur among different terminations, it is recommended that
a special dial-up port be designated for trunk testing. However, it should be recognized that even
when using a single termination to test all trunks, consideration for gain tracking variation in the
dial-up port must be included. The gain tracking variation will occur because different trunk
losses will cause different signal levels at the dial-up port. The tracking variation will be limited
by the tracking error requirements at the various interfaces (see Clause 7.2)
A.4 Digital Test Port Availability
For circuit and line-up purposes, the VG should have provisions for a test port, or equivalent, that
enables 0 dBr point testing at a digital interface.
38
39
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
A.5 Hybrid Balance
1
2
3
The measurement technique described in this section is applicable to line or trunk units that
connect to 2-wire analog interfaces.
4
5
Examples of test arrangements for testing for compliance with hybrid balance requirements are
shown in Figure A1 (full-channel method) and Figure A2 (half-channel method).
6
7
When using the full-channel method (Figure A1), the impedance of the signal generator, ZG, and
the signal detector, ZO, should match the impedance of the 4-wire port.
8
9
When using the digital half-channel method (Figure A2), the detector and generator should be
equivalent digital instruments.
10
11
12
13
An analog half-channel method may also be used (similar to Figure A2). The tests can be made
via a line or trunk unit access point, or a path can be set up between the line or trunk unit and a 4wire interface. If test access is from an analog interface, the generator impedance (ZG) and the
detector impedance (ZO) should match the interface impedance.
14
15
16
Note: A Return Loss Measuring Set (RLMS), conforming to ANSI/IEEE Standard 743 is
recommended as the signal generator and detector shown in Figure A1 (or an equivalent
digital instrument for Figure A2).
17
The steps for measuring the hybrid balance are:
18
19
1. Measure the 2-to-4 wire and 4-to-2 wire loss through the hybrid at 1004 Hz, with the 2-wire
port terminated in the appropriate reference impedance.
20
21
22
2. Measure the 4-wire to 4-wire loss (echo return loss) through the hybrid at frequencies over the
range of 200 to 3400 Hz, with the 2-wire port terminated in the appropriate reference
impedance.
23
24
3. Subtract the sum of the losses determined in Step 1 from the values measured in Step 2 to
determine the hybrid balance over the specified frequency range.
25
A.6
26
27
Examples of test arrangements for testing compliance with the input impedance requirements are
shown in Figures A3 through A6.
28
The steps for measuring the input impedance are:
29
30
1. Terminate the 4-wire analog ports not under test in impedances (ZT) that match the interface
impedances.
31
32
2. Terminate the return loss measuring set with the reference impedance (ZR) for the port under
test, as defined in 8.2.1.
33
34
35
3. Measure the single frequency return loss (SFRL) and echo return loss (ERL) over the range
200 to 3400 Hz to determine compliance with the return loss requirements in Table 10
(600  ZR) or Table 11 (Complex ZR). See Annex C for the SFRL and ERL definitions.
Input Impedance
36
37
40
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
Signal Generator
4-Wire
Analog Port
ZG
2-Wire Port
Under Test
Transmit
Path
Through
Voice
Gateway
Return Loss Measuring Set
ZO
ZR
Reference
Impedance
Receive
Signal Detector
1
2
3
4
Figure A1 - Equipment Connections for Testing the Hybrid Balance
of a 2-Wire Analog Port Using the Full-Channel Method
5
4-Wire Digital
Access Port
Digital Signal
Generator
2-Wire Port
Under Test
Transmit
Path
Through
Voice
Gateway
Half Channel
Adaptor
Digital Signal
Detector
6
7
8
9
ZR
Receive
Figure A2 - Equipment Connections for Testing the Hybrid Balance
of a 2-Wire Analog Port Using the Digital Half-Channel Method
41
Reference
Impedance
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
4-Wire
Analog Port
2-Wire Port
Under Test
Reference
Impedance
ZR
Transmit
ZT
Terminating
Impedance
Receive
ZT
Terminating
Impedance
Path
Through
Voice
Gateway
Return Loss
Measuring Set
2
3
4
5
Figure A3 - Equipment Connections for Testing a 2-Wire Analog Port Input Impedance
Using the Full-Channel Method
6
7
2-Wire Port
Under Test
Reference
Impedance
ZR
Partial Path
Through
Voice
Gateway
Return Loss
Measuring Set
Half Channel
Adaptor
8
9
10
11
Figure A4 - Equipment Connections for Testing a 2-Wire Analog Port Input Impedance
Using the Digital Half-Channel Method
12
42
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
4-Wire
Analog Port
Under Test
Reference
Impedance
ZR
4-Wire
Analog Port
Return Loss
Measuring Set
Transmit
ZT
Terminating
Impedance
Receive
ZT
Terminating
Impedance
Path
Through
Voice
Gateway
Terminating
Impedance
ZT
Receive or
Transmit
2
3
4
5
Figure A5 - Equipment Connections for Testing a 4-Wire Analog Port Input Impedance
Using the Full-Channel Method
6
7
4-Wire
Analog Port
Under Test
Reference
Impedance
ZR
Return Loss
Measuring Set
Partial Path
Through
Voice
Gateway
Terminating
Impedance
ZT
Half Channel
Adaptor
Receive or
Transmit
8
9
10
11
Figure A6 - Equipment Connections for Testing a 4-Wire Analog Port Input Impedance
Using the Digital Half-Channel Method
12
43
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
A.7 Idle Channel Noise
2
3
Idle-channel noise should be measured with a 3A type noise measuring set or equivalent, with
flat or C-message weighting.
4
5
6
When testing a connection, all analog interfaces, except the one(s) being tested, should be
terminated with appropriate impedances, and all digital input ports, other than the one(s) being
tested, should be supplied with a digital equivalent of zero V.
7
8
9
10
11
Compliance with the 13 dBrnC noise requirement for D/A units should be tested by feeding
19 dBrnC of noise in digital form to the D/A unit input. This can be accomplished as shown in
Figure A7. With the switch in position 1, the noise generator output should be varied until the
D/A test set shows 19 dBrnC. With the switch in position 2, the noise measuring set indicator
should not exceed 20 dBrnC.
Digital
Connection
Nois e
Generator
2
A/D
Converter
D/A
Unit
1
D/A Tes t Set
12
13
Figure A7 - Idle-Channel Noise Test Arrangement
14
44
Nois e
Meas uring
Set
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
A.8 Longitudinal Balance
2
A.8.1 Longitudinal to Metallic Balance
3
4
5
6
The test procedure is detailed in Annex C of ANSI/TIA-470.210-C. It is recommended that a
frequency selective voltmeter is used. These tests should be conducted for only the off-hook state
of the VG.
A.8.2 Metallic to Longitudinal (Transverse) Balance
7
8
9
The test procedure is outlined in the ANSI/TIA-968-A and TIA/EIA/TSB31-B, the Part 68
Rationale and Measurement Guidelines. Test circuits that satisfies the stated conditions are
shown in Figure A8 (Analog), and Figure A9 (Digital).
10
11
12
13
A metallic voltage should be applied from a balanced source with a metallic impedance Z 0 at
suitable points over the frequency range f1 to f2, and set so that Vm equals E volts when a
termination of Z0 is substituted for the VG. The Z0 termination should then be replaced by the
VG and the longitudinal voltage Vs measured.
14
The frequency ranges and terminations for each service are defined in Table A1.
15
The conditions for performing these measurements on the VG are:
16
17
18
(a)
All values of dc loop current that the interface under test is capable of drawing when
connected to the ANSI/TIA-968-A loop simulator circuit for DEO trunk interfaces, or
the ANSI/TIA-968-A line simulator circuit for OPS and DID interfaces.
19
(b)
All reasonable conditions of application of earth ground to the VG under test.
20
21
(c)
All DEO trunk or OPS interfaces not under test, terminated in their appropriate
networks or in some cases grounded (see (h), below).
22
23
(d)
All other than DEO and OPS interfaces terminated in circuits appropriate to those
interfaces.
24
(e)
Both on-hook and off-hook states applicable to the interface under test.
25
26
(f)
Impedances of the balance test circuit should be (Z0) metallic and (Z1) longitudinal, as
defined in Table A1.
27
(g)
Termination of all interfaces not being measured should be follows:
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
DEO trunk
OPS, off-hook
OPS, on-hook
(h)
(i)
(ii)
(i)
(i)
(ii)
Figure A10
Figure A11
(unterminated).
For station line interfaces designed to isolate longitudinal currents introduced through
fully-protected premises wiring or through non-registered equipment, or both, either of
the T or R conductors of all ONS station interfaces should be grounded, and the T or R
conductors should be both:
Terminated in an impedance that will reflect correct impedance to the network port
to which it is connected for through transmission (see Figure A12).
Unterminated.
For station line interfaces not designed to isolate longitudinal currents introduced
through unprotected premises wiring, the T&R conductors of all ONS station
interfaces should be both:
Terminated in a metallic resistance of 600  and a longitudinal resistance of 150 
(see Figure A11).
Unterminated.
45
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Table A1 - Termination and Frequency Ranges
Analog voiceband
1.544 Mbps digital
Longitudinal Termination (Z1)
500 
90 
Metallic Impedance (Z0)
600 
100 
Lower Frequency (f1)
200 Hz
10 kHz
Upper Frequency (f2)
4 kHz
1.544 MHz
0.775 V
0.316 V
Metallic Voltage for Test (E)
2
3
A.8.2.1
Transverse Balance Test (Analog)
4
Tip
T1
Vs
Oscillator
Off-Hook Station
Termination
(Figs. A9 & A10 )
C3
C1
FCC Loop
Simulator
Circuit
Rs
Vm
Voice Gateway
Under Test
C2
Off-Hook Trunk
Termination
(Fig. A11 )
C4
Ring
Ground Plane
Oscillator
T1
C1, C2
C3, C4
Rs
Audio oscillator with a source impedance of 600 
WECo 111C or 119E, or ADC 118F, or equivalent
8 F, 400V dc, matched to within 0.1%
100 to 500 pF trimmer capacitor
500 
Voice gateway ground
5
6
Figure A8 - Transverse Balance Test Circuit (Analog)
7
46
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
Tip
R2
R1
R1
R2, R3
300 
300 
Voice gateway ground
R3
1
2
Ring
Figure A9 - Off-Hook Termination for OPS or Unprotected ONS Interfaces
3
4
Tip
600 
Voice gateway ground
Ring
5
6
7
Figure A10 - Off-Hook Termination for Station Interfaces with Longitudinal Current
Isolation
8
9
Tip
R2
R1
R4
R1
R2, R3
R4
R3
10
11
300 
300 
350 
Voice gateway ground
Ring
Figure A11 - Off-Hook Termination for DEO Interfaces
12
13
14
47
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Notes:
2
1. Vm should not be measured at the same time that Vs is measured.
3
4
5
2. Use trimmer capacitors C3 and C4 to balance the test circuit to 20 dB greater balance than
the equipment standard for all frequencies specified, with a 600  resistor substituted for
the VG.
6
7
3. R1 of the off-hook terminations should be adjusted to obtain a balance of 60 dB from
200 Hz to 1 kHz and  40 dB from 1 kHz to 4 kHz.
8
9
4. Exposed conductive surfaces on the exterior of the VG should be connected to the ground
plane.
10
11
5. Use the ANSI/TIA-968-A loop simulator for DEO trunks with resistor R1 of the simulator
disconnected.
12
13
6. Use the ANSI/TIA-968-A line simulator for OPS lines and DID trunks with resistor R1 of the
simulator disconnected.
14
15
7. Use the off-hook termination shown in Figure A10 for station interfaces with longitudinal
current isolation as described in Clause A.8.2 (h).
16
17
48
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
A.8.2.2
Transverse Balance Test (Digital)
2
T1
Spectrum
Analyzer
Spectrum
Analyzer
Vs
Vm
S3
RL
Tip
S1
C2
Tracking
Generator
Voice Gateway
Under Test
S2
C1
RCal
Ring
C2
Ground Plane
Tracking Generator
T1
C1
C2
RL
RCal
Tracking generator with a source impedance of 100 
1:1 100  wide-band transformer
20 pF differential capacitor
3 pF composition RF capacitor
90 non-inductive precision resistor
non-inductive precision resistor
Voice gateway ground
3
4
Figure A12 - Transverse Balance Test Circuit (Digital)
5
Notes:
6
7
8
1. Capacitor C1 should be a dual-stator, air-variable RF capacitor that maintains a constant
capacitance between stators, while providing a variable capacitance from either stator to
ground.
9
10
2. Capacitor C2 may be placed on either line of the test set (as shown), to obtain proper
balancing of the bridge.
11
49
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
A.9. Crosstalk Coupling Loss
1
2
3
4
A test arrangement for measuring crosstalk coupling loss is shown in Figure A13. It may be
desirable when making crosstalk measurements that a 10 dBrnC level of noise exist at the input
interface of the disturbed connection.
5
Test Procedure
6
7
8
(1)
Vary resistors R1 through R4 (referring to Figure A13) to obtain the full loop current
ranges specified for the VG interfaces under test, as measured by the 0-200 mA dc
meters.
9
10
11
(2)
Calibrate the 600  oscillator at 1004 Hz to a level of 0 dBm into a separate 600 
resistor. Then, reconnect the oscillator, without changing its level, into the test circuit as
shown in Figure A13.
12
(3)
Take readings on both wave analyzers in the disturbed connections:
13
14
(a)
Select the higher power reading and subtract it from the calibrated level of the oscillator.
The result is value A.
15
(b)
Interchange the oscillator and load resistor R5 and repeat (a). The result is value B.
16
17
(c)
Interchange the disturbing and disturbed connections and repeat (a) and (b). The results
are values C and D.
18
19
(d)
Select the lowest power value of A, B, C, and D. This is the value of crosstalk coupling
loss for that pair of connections.
20
(4)
Repeat (3) for all frequencies over the range 200 to 3400 Hz.
21
(5)
Repeat (4) for all loop current values according to (1).
22
(6)
Repeat (5) for all pairs of connections of the VG.
50
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
Tip
T1
Disturbing
Connection
Tip
T2
mA
Oscillator
(600 )
mA
R1
C1
Voice Gateway
Under Test
Ring
C2
R5
R2
Ring
Ground Plane
Tip
T3
Disturbed
Connection
Tip
T4
mA
WA
R6
mA
R3
C3
Voice Gateway
Under Test
Ring
C4
R4
Ring
Ground Plane
Oscillator
WA
mA
T1 to T4
R1 to R4
R5 to R7
C1 to C4
Audio oscillator with a source impedance of 600

Audio wave analyzer
0 to 200 mA ammeter
WECo 111C or 119E, or ADC 118F, or equivalent (Zin = Zout)
2 kadjustable
600 
10 F, 400V dc
1
2
Figure A13 - Crosstalk Coupling Loss Test Circuit
51
R7
WA
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Annex B (informative) - Telephony Loss Level Planning Overview
2
This annex is informative only and is not part of this standard.
3
B.1 Introduction
4
5
Telephony loss planning is concerned with the end-to-end loss between the sender and receiver
over a telephony network.
6
7
8
It is called a loss plan, as the primary purpose is to approximate the free air loss between a talker
and listener in a normal conversation. A secondary purpose is to control echo due to impedance
mismatches in connections with long delays.
9
10
11
The loss plan is also related to the optimization of signal levels in equipment involved in the endto-end connection, and to the provisions of ANSI/TIA-968-A regarding the prevention of
network harm.
12
B.2 Send and Receive Levels
13
14
15
16
17
18
19
The objective of a telephone connection is to simulate a 1 meter free air path between two
talkers. This simulation involves several objective and subjective factors that are not present in
the 1 meter air path. These include monaural listening, narrowband frequency response, the
preferred listening level and others. For any telephone connection, the optimum OLR to achieve
the preferred listening level is 10 dB. In a digital connection, the network loss is zero; therefore,
the required loudness ratings are adjusted in the send and receive sections of the digital telephone
set.
20
21
22
The send and receive levels of a telephone relate the conversion of acoustic pressure to electrical
power and vice versa. The acoustic pressure units are in dBPa (Pascals), and the electrical power
units are in dB mW.
23
24
Pressure is measured in Newtons per square meter (Pascals), and the relationship between
dBSPL and dBPa is shown Table B1.
25
Table B1 – Acoustic Levels
26
dBSPL
dBPa
Parameter
94
0
Acoustic Pressure referred to One Pascal
89.3
-4.7
Average speech level at the MRP
0
-94
Lower limit of human hearing
27
28
52
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
B.2.1 Telephone Equipment Loudness Ratings
1
2
3
4
The loudness ratings of a telephone are the unit-less acoustic-to-electrical-to-acoustic conversion
factors as shown in Figure B.1. As the acoustic and electrical units are both relative levels in
dBs, the conversion factors are also in dBs.
5
dBm
dBPa
Send Loudness
Rating (SLR)
dBm
Electrical
Loss (dB)
dBPa
Receive Loudness
Rating (RLR)
Overall Loudness Rating (OLR)
6
7
Figure B1 - Terminal Loudness Ratings
8
9
The loudness ratings of the three telephone ports defined in this standard are shown in Table B2.
10
11
Table B2 - Telephone Loudness Ratings
Telephone Port
SLR (dB)
RLR (dB)
Notes
OPS
8
-3
1
ONS
4
-7
2
DGS
8
2
3
12
13
Notes:
14
15
16
17
18
1.
The OPS loudness ratings are representative of 2500-type analog telephones operating on
26 gauge/2.75 km loops with normal 48 volt battery feed and 600 ohm termination, as
measured at a VG OPS port. See ANSI/TIA-470.110-C, Annex E for further details. OPS
loudness ratings are assumed to be the same as DEO AAL loudness ratings that have
900 ohm terminations, but it depends on the characteristics of the telephone.
19
20
21
2.
The ONS loudness ratings are representative of 2500-type analog telephones operating on
very short loops with the typical current-limited battery feed and 600 ohm termination of
VG ONS ports. See ANSI/TIA-470.110-C, Annex E for further details.
22
23
3.
The DGS loudness ratings of SLR = 8 dB and RLR = 2 dB conform to the requirements
specified in ANSI/TIA-810-B.
24
25
26
27
B.2.2 Overall Loudness Ratings
The Overall Loudness Rating (OLR) of a connection is the sum of the sending terminal SLR, any
system or network loss, and the receiving terminal RLR. This is illustrated in Figure B2 for setto-set calls within a VG.
28
29
53
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
Digital Set
Voice Gateway
Digital Set
0 dB Loss
SLR
8 dB
RLR
2 dB
OLR
10 dB
ONS Set
Voice Gateway
ONS Set
12 dB Loss
SLR
4 dB
OLR
9 dB
1
2
3
4
5
6
7
RLR
-7 dB
Figure B2 - Telephone-to-Telephone Overall Loudness Ratings
B.2.3 Optimum Overall Loudness Ratings
Figure B3 shows a plot of OLR versus R-Value using the E-Model (ITU-T Recommendation
G.107). The majority of the OLR values in Table 2 are at or above an R-Value of 90, which puts
them in the ‘very satisfied’ category. See TIA/EIA/TSB32-A for information on use of the EModel.
All other parameters at default values according to
ITU-T Recommendation G.107 (03/2003)
100
95
R-Value 90
85
80
0
2
4
6
8
10
12
14
16
OLR (dB)
8
9
Figure B3 - E-Model Optimum Overall Loudness Rating
10
54
18
20
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
2
3
4
5
6
7
B.2.4 ATT Network Interface Loudness Ratings
In Table 3, the network interface loudness ratings for the ATT port are derived from the
combination of analog POTS set loudness ratings and nominal network losses. The 0 dBr
reference point cannot be used in this case because the tie trunk is analog, but a reference point
can still be established as shown in Figure B4, at the ATT analog network interface point. Note
that the ATT network interface loudness ratings include a nominal 2 dB trunk loss in both
directions.
SLR
8 dB
RLR
1 dB
11 dB
-1 dB
-7 dB
RLR
OLR = 12 dB
Digital
Set
3 dB
2 dB
6 dB
VG
ATT Port
Analog Tie
Trunk
VG
ATT Port
0 dB
2 dB
9 dB
Analog
POTS set
OLR = 17 dB
RLR
2 dB
2 dB
15 dB
SLR
13 dB
4 dB
SLR
Reference Point
8
9
Figure B4 - ATT Network Interface Loudness Ratings
10
11
B.3 Port-to-Port Loss Allocation
12
13
14
It should be noted, that the actual allocation of the port-to-port loss to send and receive direction
directly influences the available dynamic range of the PCM coding scheme and the noise level.
This may lead to substantial impacts on speech transmission quality as perceived by the user.
15
16
Care should be taken to ensure that excessive input gain or loss does not cause either overload,
or a poor signal-to-noise ratio, at the 0 dBr point.
17
Example:
18
The ONS to OPS loss is specified as 9 dB.
19
20
21
This could be implemented (in an extreme case) as an ONS input loss of -9 dB (9 dB gain), and
an OPS output loss of 18 dB. The overall loss would be 9 dB, but the effective SLR at the 0 dBr
point would be -5 dB ([ONS SLR = 4] + [Tx loss = -9] = -5 dB).
22
23
24
25
26
27
28
SLR 8 dB = -19 dBm0 for an average talker. ONS SLR 4 dB plus 9 dB of gain means the average
talker power would be -6 dBm0. A loud talker/loud set might add another 9 dB raising the power
to +3 dBm0, which is the codec overload level point, where clipping occurs. Voice peaks are
about 12 dB higher than the average level, so the average talker would have peaks at +6 dBm0,
3 dB above the clipping point and the loud talker would be always be clipping. Obviously,
adding 9 dB of transmit gain followed by 18 dB of attenuation is the wrong strategy for this
connection. The correct approach is 3 dB of transmit loss, followed by 6 dB of receive-side loss.
55
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
B.4 DTMF Overload on Analog Trunks
2
3
4
5
There is a potential for codec overload on the analog trunk interface when using the FXO to
WAN setting, and in-band DTMF signaling is used for voice mail access, credit card verification,
etc. This is only likely to happen in the situation where both the subscriber doing the signaling
and the VG are close to the central office.
6
7
8
9
10
11
12
13
Given that some subscribers are going to be located close to the central office, the decision on
when to introduce additional loss in the VG analog trunk interface has to be based on the
distance of the VG from the central office. The generally excepted definition of a short loop is
2 km or less (less than approximately 3 dB loss), and therefore the recommendation is that an
additional 3 dB of loss be inserted in the analog trunk interface for short loops when making
FXO-to-WAN connections. The simplest way to do this is to use the FXD/WAN setting. This
will also have the added advantage of reducing the OLR of the connection to a more comfortable
level.
14
15
16
17
18
19
20
Figure B5 illustrates the subscriber to VG losses, and the resultant DTMF level at the analog
trunk interface, for both long and short loops. It is assumed that the analog set is transmitting
DTMF signals at the maximum level of 0 dBm, rather than the nominal level of -2 dBm and that
the DEO is still using the old loss plan with the A/D pad = 0 dB and the D/A pad = 0 dB (the
lowest loss option). If the new DEO loss plan in T1.508 (2003), with A/D pad = 0 dB and the
D/A pad = 6 dB, was used then this DTMF overload issue would be eliminated. However, this
would require that VG installer know which version of T1.508 the DEO used.
Analog Set Connected via an Analog Trunk (Long Loop)
DTMF Level
0 dBm
Loss
-0.5 dBm
-0.5 dBm
-3.0 dBm
3.0 dBm
0.5 dB
0 dB
2.5 dB
-6 dB
PSTN Subscriber
Line
2500
Analog Set
Analog Trunk
FXO to
DEO
0.35 km
WAN
Voice
Gateway
2 km
Analog Set Connected via an Analog Trunk (Short Loop)
DTMF Level
0 dBm
Loss
-0.5 dBm
-0.5 dBm
-1.0 dBm
2.0 dBm
0.5 dB
0 dB
0.5 dB
-3 dB
PSTN Subscriber
Line
2500
Analog Set
Analog Trunk
0.35 km
21
22
FXD to
DEO
WAN
0.35 km
Figure B5 - DTMF Levels for Long and Short Loop Analog Trunks
23
24
56
Voice
Gateway
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
2
3
4
B.5 Open Loop Loss and Network Stability
Annex A6 of TIA/EIA/TSB32-A provides an overview of 4-wire loop stability or ‘Singing’. The
fundamental principle is that a 4-wire loop will oscillate if the sum of all losses and gains around
the loop at one single frequency is equal to or less than 0 dB.
5
6
B.6 Reference Levels
7
B.6.1 Zero-Level Point
8
9
10
11
The zero-level point (ZLP) generally represents the digital (PCM) switching point in a VG. A
0 dBm0 signal at this point will decode to 0 dBm, or 1 mW in 600 The “B” revision of this
standard replaced the term “zero-level point” with the term “0 dBr point”.
B.6.2 0 dBm0 Definition
12
13
14
The 0 dBm0 level corresponds to the digital milliwatt (DMW) and is defined as the absolute
power level at a digital reference point of the same signal that would be measured as the absolute
power level, in dBm, if the reference point was analog.
15
16
17
The absolute power in dBm is defined as 10 log (power in mW/1 mW). When the test impedance
is 600  resistive, dBm can be referred to a voltage of 775 mV, which results in a reference
active power of 1 mW.
18
0 dBm0 corresponds to an overload level of approximately 3 dBm in the A/D conversion.
19
B.6.3 Digital Milliwatt
20
21
The digital reference level is the Digital Milliwatt (DMW) as defined in ITU-T Recommendation
G.711, Tables 5 (A-law) and 6 (-law).
22
23
A 1 kHz signal at a nominal value of 0 dBm0 will be present at the output of a perfect codec if
the periodic PCM code sequence specified in Table 5 or 6 is present at the input of the decoder.
24
25
26
The use of an exact 1 kHz signal can cause problems with some transmission and measuring
equipment, so digital periodic sequences representing reference frequencies of 1004 Hz (IEEE)
or 1020 Hz (ITU) are generally used instead.
27
These reference signals can be at either -10 dBm0 or 0 dBm0 +/- 0.03 dB.
28
B.6.4 Transmission Level Translation
29
30
31
The requirements in this standard that are affected by signal level are specified with respect to
the 0 dBr point. The gain or loss from the port interface to the 0 dBr point has to be taken into
account when making measurements.
32
33
In the case of input ports, the input level should be increased or decreased by the amount
equivalent to the loss or gain from the interface to the 0 dBr point.
34
35
In the case of output ports, the output measurement should have an amount equivalent to the loss
or gain from the 0 dBr point to the Interface, added or deleted.
36
37
38
Note: This amount is not the same as the loss specified in Table 1 and Table 2, as these loss
requirements are for port-to-port connections, and the port-to-0 dBr-to-port losses and gains are
defined by the VG manufacturer.
39
40
It is generally easier to set up the test connection as an analog-port to digital-port connection,
although this is not a requirement.
41
42
43
57
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Example:
2
Output Interface – Idle-Channel Noise
3
4
Requirement: The 3-kHz flat weighted noise should not exceed 35 dBrn on 50 percent of
the connections.
5
6
7
8
Given the case of a DAL to OPS port, and assuming the manufacturer has implement the 6 dB
loss in the OPS interface, then the maximum allowable noise level would be adjusted by 6 dB, as
shown below:
9
10
11
12
13
0 dBr
Point
OPS
Interface
Noise
Measuring Set
0 dBm0
6 dB Loss
29 dBrn max.
14
58
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Annex C
2
This annex is informative only and is not part of this standard
3
4
5
6
C.1 Echo Return Loss (ERL)
Echo return loss (ERL) is a weighted average of the return loss values over the frequency range
400 to 3400 Hz. Frequency multiples of 8 kHz must be avoided; the table below shows one
convention for avoiding multiples. ERL is calculated as follows:
 RL( f i )
 N

10
 W( f i )10

ERL  10log10 i 1 N
dB
  W( f i )


i1

7
8
(informative) - Loss Definitions
where
RL f i   Return loss or transhybrid loss, in dB, at frequency f i ,
9
10
W  f i   Weighting factor at frequency f i (see the following table ).
Frequency
fi (Hz)
ERL Weights
W(fi)
402
0.0631
602
0.6761
803
1.0000
1004
1.0000
1205
1.0000
1405
1.0000
1606
0.9550
1807
0.7586
2008
0.4467
2208
0.1995
2409
0.0813
2610
0.0324
2811
0.0129
3011
0.0051
3212
0.0021
3413
0.0009
59
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
2
3
4
C.2 Return Loss (RL)
Return loss (RL) at an impedance discontinuity in a transmission path is the ratio (in dB) of the
power level of an incident signal to the power level of the resulting reflected signal. The general
expression for return loss is:
5
ZI + ZR
RL = 20 Log
ZI - ZR
6
7
8
dB
where ZI and ZR are the input and reference impedances respectively.
9
10
Single-frequency return loss (SFRL) is the lowest value of non-weighted return loss occurring in
the frequency range 200 to 3200 Hz.
11
12
Single-frequency transhybrid loss (SFTHL) is the lowest value of loss, from the input pair to the
output pair of the same 4-wire interface, occurring in the frequency range 200 to 3200 Hz.
13
14
15
C.3 Transhybrid Loss (THL)
Transhybrid loss (THL) is the loss from the input pair to the output pair of the same 4-wire
interface.
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SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Annex D
(informative) - Pan-European Loss and Level Plans - ES 202 020
2
D.1
3
D.1.1 Voice Gateway Connections
4
5
6
7
The Pan-European Half-Channel Loss Plan
Figure D.1 illustrates the connection types for a typical Pan-European VG application. There
may be other applications not covered by this diagram, but sufficient information is provided for
users to determine the applicable connection types for their particular application, and the
corresponding interface losses to be applied.
8
Packet Connection
Packet Facilities
TDM Connection
Analog Connection
WAN
WAN
IP Network
Ports
MD
Digital
Public
Exchange
K2
KD
Public
Switched
Network
Ports
Private
Network
Ports
Voice
Gateway
Telephone
Ports
MD
M2
M4
L22
LD
L21
LD
9
10
Figure D.1 - Pan-European Voice Gateway Connections
11
61
Voice
Gateway
PBX
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
D.1.2 Interface Descriptions
2
Telephone Interfaces
3
L2 – 2-wire Analogue
4
5
6
7
The L2 interface provides for the connection of 2-wire analogue extension lines and will carry
signals such as speech, voice-band analogue data and DTMF signals, etc. In addition, the
interface L2 provides for ordinary functions such as direct current (DC) feeding, DC signalling,
ringing, etc.
8
9
10
Note: The L2 interface is subdivided into short lines and long lines for transmission planning
purposes. These are designated L21 and L22 respectively, and are equivalent to the North
American ONS and OPS ports.
11
LD – Digital
12
13
The LD interface is a digital extension interface used to connect terminals which are also
intended to be connected directly to digital interfaces of the public switched network.
14
Public Network Interfaces
15
K2 – 2-wire Analogue
16
17
The K2 interface provides for the connection of 2-wire analogue subscriber lines between a VG
and a public exchange.
18
KD – Digital
19
The KD interface provides for the connection of a digital access to the public switched network.
20
Private Network Interfaces
21
M2 – 2-wire Analogue
22
23
The M2 interface provides for the connection to 2-wire analogue circuits (e.g. leased lines)
between a VG and a PBX.
24
M4 – 4-wire Analogue
25
26
The M4 interface provides for the connection to 4-wire analogue circuits (e.g. leased lines)
between a VG and a PBX.
27
28
Note: The M4 interface is used as the generic private network analogue interface for loss
planning purposes. The required losses for the M4 and M2 interfaces are the same.
29
MD – Digital
30
The MD interface provides for connection to a system specific (digital) inter-VG circuit.
31
32
Note: The MD interface shares the KD designation for loss planning purposes (they are both
digital connection with zero loss).
33
Packet Network Interfaces
34
WAN – Wide Area Network
35
A WAN interface connects from VGs to packet-based wide area networks.
36
37
38
Note: The term WAN is used in the same context as the public switched network, in that it
represents connections between geographically separated VGs. It should be noted that WAN and
LAN are synonymous from a transmission perspective.
39
40
41
D.1.3 Voice Gateway Half-Channel Loss Plan
Table D.1 shows the VG half-channel loss plan for the Pan-European region, given in equivalent
loudness ratings and respective loss.
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1
Table D.1: Voice Gateway Half-Channel Loss Plan
2
WAN
0 dBr Point

(dB)
L21
L22
LD
WAN
KD
K2
M4
a
b
SLR
Tx
Loss
5
23
0
0
0
-6
-2
3
6
8
8
8
16
10
c
=(a + b)
SLRHC
d
=(e + f)
RLRHC
8
8
8
8
8
101
8
2
2
2
2
2
4
2
e
f
Rx
Loss
10
7
0
0
0
-1
-2
RLR
g
=(c + d)
OLR2
-8
-5
2
2
2
5
4
10
10
10
10
10
14
10
h
=(8 + d)
Desirable
OLR2
10
10
10
10
10
12
10
3
4
5
Column a
shows the SLR of the telephone and trunk between the acoustic interface and the
connection point to the VG.
6
Column b
shows the VG transmit loss required to achieve the required SLRHC at the 0 dBr point.
7
Column c
shows the resulting Half-Channel SLR (SLRHC) at the 0 dBr point (WAN).
8
Column d
shows the resulting Half-Channel RLR (RLRHC) at the 0 dBr point (WAN).
9
10
Column e
shows the VG receive loss required to achieve the desirable OLR, based on the RLR
shown in column f, and the optimum SLR of 8 dB.
11
12
Column f
shows the RLR of the telephone and trunk between the acoustic interface and the
connection point to the VG.
13
Column g
shows the resulting OLR, based on the actual SLR.
14
Column h
shows the desirable OLR, based on the optimum SLR of 8 dB.
15
16
Note 1: It is not possible to achieve the optimum SLRHC of 8 db for connections from analogue
networks due to the potential for loop instability.
17
18
Note 2: The OLR values shown in the table are as perceived by the listener, i.e., this is shown as
a one-way connection.
19
20
21
22
Note 3: Although this Standard does not apply to Local Exchanges, in some situations, the same
product may be capable of being either a VG or a Local Exchange. Loss plan designers should
be aware of the subtle difference between the two loss plans: The L2 Tx loss at a Local Exchange
is 0 dB, rather that the 2 dB for an L22 Tx loss at an Enterprise Voice Gateway.
23
24
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1
D.2
The Pan-European Full-Channel Loss Plan
2
Full-Channel Loss Plan Interpretation
3
4
5
Table D.2 shows the interface-to-interface loss in the Pan-European full-channel loss plan.
Arrows at the row and column designators indicate the transmission direction in which the coordinate loss values are to be inserted.
6
7
8
For example, co-ordinate 1 B indicates a nominal interface-to-interface loss of 12 dB from the
L21 interface to the L22 interface, and co-ordinate 2A indicates a 12 dB loss in the other
direction, from the L22 interface to the L21 interface.
9
Note: This is a loss plan, therefore negative values denote gain; e.g., -6 indicates 6 dB gain.
10
Table D.2: Voice Gateway Full-Channel Loss Plan (Pan-European)
A
B
C
D
E
F
G
L21
L22
LD
WAN
KD/MD
K2
M4
Loss (dB)







1
L21

15
12
5
5
5
4
3
2
L22

12
9
2
2
2
1
0
3
LD

10
7
0
0
0
-1
-2
4
WAN

10
7
0
0
0
-1
-2
5
KD/MD

10
7
0
0
0
-1
-2
6
K2

4
1
-6
-6
-6
-7
-8
7
M4

8
5
-2
-2
-2
-3
-4
11
12
Note: The interface-to-interface losses are the sum of the transmit and receive half-channel
losses defined in Table D.1.
13
Full-Channel Loudness Ratings Table Interpretation
14
15
16
17
Table D.3 is provided to show the relationship between OLR, SLR, RLR and interface-tointerface loss. For example, for an L21 to L22 connection, the L21 SLR is 3 dB, the VG loss is
12 dB (from 1B in Table B.1), and the L22 RLR is -5 dB. The overall loudness ratings is
therefore 3 + 12 - 5 = 10 dB.
18
Table D.3: Voice Gateway Full-Channel Loudness Ratings (Pan-European)
L21
L22
LD
WAN
KD/MS
K2
M4
RLR
-8
-5
2
2
2
5
4
SLR
OLR







L21
3

10
10
10
10
10
12
10
L22
6

10
10
10
10
10
12
10
LD
8

10
10
10
10
10
12
10
WAN
8

10
10
10
10
10
12
10
KD/MS
8

10
10
10
10
10
12
10
K2
16

12
12
12
12
12
14
12
M4
10

10
10
10
10
10
12
10
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1
Annex E
(informative) - Loss Plan and Loudness Rating References and Hierarchy
G.101
SLR 8 dB1
RLR 2 dB
OLR 10 dB
Digital
Analog
TIA-810-B
SLR 8 dB
RLR 2 dB
TIA-470.110-C
SLR 8 dB
RLR -3 dB
@ 2.7 km
T1.508
Loss A/D 0 dB
Loss D/A 6 dB
TIA-912-B
Loss A/D 0 dB
Loss D/A 6 dB
TIA-464-C
TIA-464-C-1
Loss A/D 0 dB
Loss D/A 6 dB
T1.508
Loss D/D 0 dB
Loss D/D 0 dB
SLR = SLRset + Loss A/D = 8 + 0 = 8 dB
RLR = RLRset + Loss D/A = -3 + 6 = 3 dB
OLR = SLR + Loss A/D + Loss D/D + Loss D/A + RLR
= 8 + 0 + 0 + 6 - 3 = 11 dB
2
3
TIA-920
SLR 8 dB
RLR 2 dB
TIA-912-B
Loss D/D 0 dB
Loss D/D 0 dB
TIA-464-C
TIA-464-C-1
Loss D/D 0 dB
Loss D/D 0 dB
SLR = SLRset + Loss D/D = 8 + 0 = 8 dB
RLR = RLRset + Loss D/D = 2 + 0 = 2 dB
OLR = SLR + Loss D/D + RLR = 8 + 0 + 2 = 10 dB
Where: SLR and RLR are at the 0 dBr point.
Note 1: According to ITU-T Recommendation G.100.1, Clause 6.3, SLR > 2 dB
gives reasonable protection against objectionable speech clipping.
Figure E.1 – Hierarchical Relationship between Loudness Rating and Loss Plan Standards
65
SP-3-4826-RV2 (to be published as ANSI/TIA-912-B)
1
Annex F
2
3
4
5
The effects of impairments introduced by IP networks are described in TIA/TSB-116-A, Voice
Quality Recommendations for IP Telephony. The effects of impairments are evaluated using the
E-model, which includes the effects of both the terminal equipment (end points) and the
transmission network.
6
7
IP networks impact two of the impairment parameters; end-to-end delay and packet loss.
Unfortunately both these have significant effects on speech quality.
8
9
A VG is also likely to perform TDM/IP conversions, and will need to employ echo cancellers if
there are any 2-to-4 wire converters on the TDM side of the conversion.
F.1 Delay
10
11
(informative) - IP Transmission Impairments
End-to-end delay is a combination of the:
12

The sending end point encoding and packetizing delay,
13

The network processing and propagation delay,
14

The receiving end point jitter buffer, depacketizing, and decoding delay.
15
16
17
There is an interaction between the network delay and the receiving end point delay, in that the
end point has to compensate for network delay variances via a jitter buffer, and increased
variances lead to longer average delay in the end point.
18
Note: Other processes such as transcoding or encryption will also add delay.
19
20
21
22
23
F.2 Packet Loss
Packets can be lost either in the network, or can be discarded by the end point because they are
too late (delayed beyond the range of the jitter buffer). In this case there is an interaction between
network delay variances and packet loss in the end point.
F.3 Voice Gateways and Network Performance
24
25
The purpose of standards for voice transmission is to ensure that voice quality is achieved by
adherence to the standards.
26
27
In a PBX standard, the TDM transmission and switching is a dedicated resource within the PBX
framework, and under normal conditions has little or no impact on voice quality.
28
29
30
31
In a VG standard, transmission and switching is via IP networks, which can introduce
impairments as noted above, and may also be shared by other entities beyond the control of the
VG. Ensuring good voice quality will therefore require the use of managed networks and other
techniques, which is beyond the scope of this standard.
32
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1
F.4 Voice Quality of Service
2
3
4
There are a number of standards groups addressing the issue of voice quality of service (QoS).
Users of this standard should ensure they are familiar with the work of these groups, as the
methods and techniques for managing voice QoS are constantly evolving.
5
Some of the major groups involved in IP telephony voice QoS are listed below:
6
TIA
Telecommunications Industry Association
7
www.tiaonline.org
8
TR-41
User Premises Telecommunications Requirements
9
10
ATIS Alliance for Telecommunications Industry Solutions
11
http://www.atis.org/
12
PRSSC
Performance, Reliability, and Security Standards Committee
13
14
IETF Internet Engineering Task Force
15
www.ietf.org
16
MPLS
Multiprotocol Label Switching
17
DIFFSERV
Differentiated Services
18
19
20
ITU-T International Telecommunication Union - Telecommunication Standardization
Sector
21
www.itu.int/ITU-T
22
ITU-T SG 12
End-to-end transmission performance of networks and terminals
23
24
ETSI European Telecommunications Standards Institute
25
www.etsi.org
26
27
TISPAN
Telecommunications and Internet converged Services and Protocols for
Advanced Networking
28
STQ
Speech Processing, Transmission and Quality Aspects
29
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1
Annex G (informative) - Bibliography
2
3
4
[G1] ANSI/TIA-470.210-C
Requirements.
(April
2004),
Resistance
and
Impedance
Performance
5
[G2] TIA/EIA/TSB31-B (February 1998), Part 68 Rationale and Measurement Guidelines.
6
7
[G3] TIA/EIA/TSB32-A (December 1998), Overall Transmission Plan Aspects for Telephony in
a Private Network.
8
[G4] TIA/TSB-116-A (March 2006), Voice Quality Recommendations for IP Telephony.
9
10
[G5] IEEE 743-1995, Standard Methods and Equipment for Measuring the Transmission
Characteristics of Analog Voice Frequency Circuits.
11
12
[G6] ITU-T Recommendation G.100.1 (11/01), The use of the decibel and of relative levels in
speechband telecommunications.
13
14
[G7] ITU-T Recommendation G.107 (03/05) and Amendment 1 (06/06), The E-Model, A
Computational Model for use in Transmission Planning.
15
16
68
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17