Telecommunications Industry Association
TR41.1.1-06-02-006
Document Cover Sheet
Project Number
PN-3-0191
Document Title
Research of Ringer Loads in other Standards
Source
AST Technology Labs, Inc.
Contact
Name:
Don McKinnon
Phone:
321-254-0268
Complete
Address:
1430 Sarno Rd
Fax:
321-254-9511
Melbourne, FL 32935
Email:
dmckinnon@asttechlabs.com
TR-41.1.1
Distribution
Intended Purpose
of Document
(Select one)
X
X
For Incorporation Into TIA Publication
For Information
Other (describe) – Incorporate into Document as an Informational Annex
The document to which this cover statement is attached is submitted to a Formulating Group or
sub-element thereof of the Telecommunications Industry Association (TIA) in accordance with the
provisions of Sections 6.4.1–6.4.6 inclusive of the TIA Engineering Manual dated March 2005, all of
which provisions are hereby incorporated by reference.
Abstract
The following is the research result of ringer loads referenced in several Telcordia,
TIA and ATIS documents. The purpose of this is to document a historical basis for
the 5 REN 1386 ohms in series with a 40 uF capacitor load utilized in the PN-30191 draft document.
Table Of Contents
1.
Research Overview.......................................................................................................................... 2
Annex A
Ringer Loads Used in other Standards ................................................................................... 3
A.1
Ringer Loads in Various Industry Documents ............................................................................. 3
A.2
Additional Information about Ringer Loads ................................................................................. 5
A.2.1
BRIEF: Reducing 5 REN requirement to 3 REN ..................................................................... 5
A.2.2
BRIEF: Rational for Ring Trip Immunity Network.................................................................... 5
v1.0 – 20050426
Telecommunications Industry Association
1.
TR41.1.1-06-02-006
Research Overview
A. For the Ringer Pre-Trip immunity test load, network documents for DLC and Central
Office Equipment use 10K ohms, in parallel with a capacitance (2uf), in parallel with
a 1400 ohm “Ringer Load”.
B. For Ringer Pre-Trip immunity, PBX document TIA-464-C uses 15K ohms, in parallel
with a 1400 ohm “Ringer Load”.
C. The parallel 2uf capacitance for the network pre-trip immunity load is for a “very long
and very leaky loop”.
D. The 1400 ohm Ringer Load in the various documents are not all in agreement.
Some have it defined as 1386 ohms in series with a 40 uF capacitor, others as five
C4A ringers (110H at 3650 ohms + 0.45uF) and one even as a capacitance of 6 uF.
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Telecommunications Industry Association
Annex A
A.1
TR41.1.1-06-02-006
Ringer Loads Used in other Standards
Ringer Loads in Various Industry Documents
Document
GR-57CORE
Issue 1,
October 2001
(DLC)
GR-57CORE
Issue 2,
1993
5 REN Load
Ring Pre-trip Load
[5 REN Load = 1386 ohms + 40uF]
[10 kohms // 2uF // 5 REN Load]
5.4.8 Ringing Capability
A ringing load of 1 REN (Ringer Equivalent
Number) has an impedance of 7000 ohms at
20 Hz. Thus, a load of 5 REN has an
impedance of 1400 ohms at 20 Hz. A 1386
ohm resistor in series with a 40 μF
capacitor should be used as a 5 REN load
for the above criteria.
5.4.5 Ring Trip Immunity
R5-136 [539] A RT line unit shall not trip
ringing when it applies an alerting signal to a
termination of 5 REN in parallel with 10
kohms in parallel with 2 μF applied tip-toring directly at the output of the RT unit. A
termination of 5 REN is defined as 1386
ohms in series with a 40 μF capacitor…
5.4.8 Ringing Capability
Same as above
5.4.5 Ring Trip Immunity
[10 kohms // 8uF]
Note: See item A.2.2 (last page) for
additional information on this load.
(TR-NWT000057)
GR-506CORE
ISSUE 1, JUNE
1996
[5 REN Load = 1386 ohms + 40uF]
[10 kohms // 2uF // five C4A ringers]
14.1.1 Ringing Source Criteria
R14-6 [544]An SPCS shall provide a
minimum ringing voltage of 40 V rms
across a ringing load of 5 REN at the end of
any access line with a loop resistance ≤ (Rdc
– 400) ohms. Part 68 of the FCC Rules and
Regulations require that all registered
customer installation equipment that can
affect on-hook impedance have a Ringer
Equivalence Number (REN). A ringing load
of 1 REN for equipment designed for 20 Hz
ringing has an impedance of 7000 ohms at
20 Hz. Thus, a load of 5 REN has an
impedance of 1400 ohms at 20 Hz. A 1386
ohm resistor in series with a 40 μF
capacitor should be used as a 5 REN load
for the above criteria.
14.1.1 Ringing Source Criteria
R14-23 [561]The alerting signal shall not be
removed when applied to a zero-ohm loop
with the following components connected in
parallel from the ring conductor to the tip
conductor of the interface.
…— 2 microfarad capacitor;
…— 5 C4A ringers;
…— 10,000 ohm resistor.
Page 3
Notes:
1. The C4A ringers are not defined in this
document and no reference was
provided.
2. See T1.401 section for the C4A
definition.
Telecommunications Industry Association
Document
TR41.1.1-06-02-006
5 REN Load
Ring Pre-trip Load
[5 REN Per TR-NWT-000057]
[10 kohms // 6uF]
GR-909CORE
4.5.9 Ring Trip Immunity
R4-156 [202] Ringing shall not be tripped
when an alerting signal is applied to a
termination consisting of 10 kohms in
parallel with 6 μF applied tip to ring
directly at the output of the ONU.
Issue 1
March 2000
(FITL)
R4-157 [203] Ringing shall not be tripped
when a 200 Ω resistance is applied for 12 ms
or less directly at the output of the ONU.
[Not Defined]
[15 kohms // 1400 ohms (not
defined)]
Note: Section 5.4.3.1.1 PBX ringing states
5.4.5 Ringing Pre-trip
shall comply with Table 10.
To assure adequate protection against false
Table 10 - PBX Ringing Voltage Ranges ringing trip, the PBX ringing trip circuit shall
not trip ringing when tested under the
and Terminating Impedances
following conditions:
Ringing Terminating Ringing
Frequency Impedance Voltage
(Hz)
(V rms)
(Ω)
TIA-464-C,
2002
17 – 23
10,000/(N)
55 - 130
20
8,000/(N)
40 - 130
27 – 33
10,000/(N)
95 - 130
Where (N) = the number of station ringer
equivalence with which the PBX is designed
to work.
(1) A terminating impedance simulating
on-hook impedance, connected across
the station line conductors and
composed of the parallel combination
of 15 kΩ resistance and a series
connection of resistance and
capacitance whose impedance at the
specified frequency is as shown in
Table 11. (=1400 ohms)
Note: Section 5.4.6.1 Recognition of Idle
Condition
5.4.6.1.1 The PBX shall recognize a
resistance of greater than 15 kΩ tipto-ring at the station interface as an
on-hook signal.
[Not Defined]
[Not Defined]
Notes:
T1.4012001
1. Does state use of C4A ringer load for
NI Pulse Dialing criteria.
C4A = 110H at 3650 ohms + 0.45uF
2. GR57 also states the same text as
T1.401-2001 for pulse acceptance
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Telecommunications Industry Association
A.2
TR41.1.1-06-02-006
Additional Information about Ringer Loads
Additional information was found in a Telcordia Report of Issues, GR-57 ILR.
A.2.1
BRIEF: Reducing 5 REN requirement to 3 REN
PROPOSAL(S):
The 5 REN load was set by the FCC in cooperation with AT&T (which at the time owned all of the
Bell Companies) and Independent Telcos. This requirement insured that residential customers
would be able to connect five 500-type telephone sets to one POTS line. Each 500-type set contained
a C4A ringer with an equivalent REN equal to 1.
The FCC definition of a 1 REN load specifies the magnitude at 7000 ohms at 20 Hz. TR-57 Issue 2
specifies a specific R-C combination that has a 7000 ohm magnitude of impedance at 20 Hz. A REN
loading requirement of less than 5 could conceivably be specified given that the majority of the embedded
telephone station sets probably have a REN of less than 1 (e.g., 0.6). The ability to ring a customer line
with 5 telephone stations sets is probably still desirable, but the corresponding REN load could be
decreased to something on the order of 3 REN.
A preliminary investigation, however, seems to indicate that there are other industry documents (most
notably FCC Part 68, Section 3121, and TIA/EIA-470-B) that allow telephone terminal equipment to have
a REN of 1. This suggests that any change in GR-57-CORE REN load requirements would need to occur
in conjunction with these other industry groups (i.e., the TIA and ATIS).
PROPOSAL BENEFIT(S): Cost reductions in network equipment could be obtained if a smaller
capacitive load could to be support per analog line. The current proposal, however, is to take no action
at this time to reduce the GR-57 specified 5 REN load because of the need to coordinate such an
effort with other industry groups.
A.2.2
BRIEF: Rational for Ring Trip Immunity Network
What is the logic in selecting this current pre-trip test load? 8uF in parallel with 10K is an extreme test
condition when compared to the actual application. This may limit the use of more creative and less
costly ring trip schemes.
DESCRIPTION:
Requirement (R-11) in GR-57-CORE Section 5.4.5, Ring Trip Immunity, states:
(R-11) A RT line unit shall not trip ringing when it applies an alerting signal to a termination of 10K
ohms in parallel with 8 μF applied tip-to-ring directly at the output of the RT unit.
PROPOSAL(S):
As best as can be determined, this network was developed as follows:
A 5 REN load, if purely capacitive, would be about 6 μF. A very long and very leaky loop could add
an additional 2 μF. DLC systems are required to recognize 10 kilohms or greater as on-hook.
Note that GR-909-CORE has a ring-trip immunity network of 10 kilohms in parallel with 6 μF. This
would probably need to be made consistent with any changes made to GR-57-CORE.
Given the above explanation the following new Ring Trip Immunity Network is proposed:
(R-11) A RT line unit shall not trip ringing when it applies an alerting signal to a termination of 5 REN in
parallel with 10K ohms and in parallel with 2.0 μF applied tip-to-ring directly at the output of the RT unit.
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Telecommunications Industry Association
TR41.1.1-06-02-006
Where 5 REN is defined as 1386 ohms in series with a 40μF capacitor (in accordance with Section 5.4.8
(R-23)).
10k-ohms is specified for the same reason as in the existing immunity network (i.e., it’s the lower
bound of an on-hook condition for DLCs). 2μF (with no series resistor) is really a worst case
condition since loop capacitance is a distributed capacitance (i.e., you get a ~82 ohms resistance in
series with the capacitance for every 1000 feet of 26 ga cable).
Page 6