®
Inter-Tel 3000
T1 Technical Training
Self-Study Course
©Inter-Tel, Inc. 2007 All rights reserved.
Inter-Tel 3000 T1 Training Self-Study Course
Table of Contents
ABOUT THIS COURSE.................................................................................................... 1
Taking the Course ...................................................................................................... 1
Taking the Exam......................................................................................................... 1
INTRODUCTION TO INTER-TEL 3000 T1....................................................................... 3
UNDERSTANDING ISDN, T1, AND PRI .......................................................................... 5
T1 Overview ................................................................................................................ 5
Termination Equipment .............................................................................................. 5
Channel Banks........................................................................................................... 6
Pulse Code Modulation.............................................................................................. 8
D4 Frame ................................................................................................................... 9
Ordering T1 ............................................................................................................... 11
D4 Superframe......................................................................................................... 11
Extended Superframe Format (ESF) ....................................................................... 12
Coding Methods ....................................................................................................... 14
Channel Service Unit ............................................................................................... 17
Repeaters ................................................................................................................ 19
Network Timing ........................................................................................................ 21
Channel Pulse Stuffing ............................................................................................ 23
Jitter and Timing Inaccuracies ................................................................................. 23
Testing Network Systems ........................................................................................ 24
T1 Networks .............................................................................................................. 26
Point-to-Point T1 Networks ...................................................................................... 26
Point-to-Point Multiple Links .................................................................................... 27
Point-to-Multipoint Networks .................................................................................... 28
Star Networks .......................................................................................................... 29
Ring Networks.......................................................................................................... 29
Mesh Networks ........................................................................................................ 30
T1 Services ............................................................................................................... 31
LATAs ...................................................................................................................... 31
Method of Access .................................................................................................... 32
ISDN Overview.......................................................................................................... 34
Primary Rate Interface (PRI).................................................................................... 35
ISDN Hardware Definitions...................................................................................... 36
ISDN Reference Points ............................................................................................ 37
D Channel Signaling ................................................................................................ 38
INSTALLING T1 ON INTER-TEL 3000 .......................................................................... 41
Supported Switch Types ......................................................................................... 41
System Installation Steps........................................................................................ 42
i
Inter-Tel 3000 T1 Training Self-Study Course
PROGRAMMING T1 ON THE INTER-TEL 3000 ........................................................... 45
T1 Channel Programming........................................................................................ 45
PRI Channel Programming...................................................................................... 47
Line Programming for T1......................................................................................... 48
Equipped Lines ........................................................................................................ 48
Outgoing Groups...................................................................................................... 48
GLOSSARY OF TERMS ................................................................................................ 49
PRACTICE EXAM QUESTIONS .................................................................................... 57
SAMPLE T1 ORDER FORMS ........................................................................................ 63
ii
Inter-Tel 3000 T1 Training Self-Study Course
About This Course
This course is provided as a supplement to basic Inter-Tel 3000 training. It is
assumed that those taking this course are already familiar with basic telephony
and the Inter-Tel 3000 system.
After completing this course you should be able to:
•
Understand ISDN, T1, and PRI services
•
Install the T1/PRI Module
•
Program the Inter-Tel 3000 T1 features
Taking the Course
Study all the provided material carefully.
Also refer to the Inter-Tel 3000 documentation as your study guide. It is essential
to understanding the Inter-Tel 3000 system.
Taking the Exam
The Inter-Tel 3000 T1 exam is available on your training CD or online at:
www.inter-tel3000.com
The exam questions were developed to test your full understanding of T1/PRI on
the Inter-Tel 3000. After studying the material, complete the exam. Answer each
question, referring to this course to find the best answer.
If you receive a passing score of 80% or higher, you will be directed to fax your
results to Inter-Tel University so that your certification can be added to Inter-Tel’s
computerized certification list.
If you do not pass the exam, you will be given an opportunity to repeat it and
improve your test score.
Being certified on Inter-Tel 3000 T1 entitles you to call Inter-Tel’s Technical
Support department when you need assistance. Your certification will be verified
at the start of your call.
IMPORTANT
You must complete this course and pass the exam to receive Inter-Tel 3000 T1
certification. Without Inter-Tel 3000 T1 certification you will not be able to receive
Technical Support on T1 matters.
1
Inter-Tel 3000 T1 Training Self-Study Course
2
Inter-Tel 3000 T1 Training Self-Study Course
Introduction to Inter-Tel 3000 T1
Inter-Tel 3000 versions 3.0 and higher support T1 Primary Rate Interface (PRI)
services using the Inter-Tel 3000 T1/PRI Module. That means that you can
choose digital trunk connection (T1 or PRI) instead of analog trunk connection.
Features and benefits of Inter-Tel 3000 T1/PRI Module:
•
Additional bandwidth on network connections enabling richer and faster
out-of-band signaling for voice and/or data.
•
Combined voice and/or data to provide cost savings and streamline
resource management.
Digital voice and data trunk connection can be established on Inter-Tel 3000 one
of three ways:
•
T1 Connection: If you purchased a voice-only T1 service from the ISP,
the T1/PRI Module can be connected to provide voice connection without
an external CSU.
•
PRI ISDN: If you purchased PRI service from your Internet Service
Provider (ISP), the T1/PRI Module can be used to provide voice
connection, and may be used to provide data connection on a dial-up
basis.
•
External Channel Service Unit (CSU): If you purchased a T1 service for
voice and data from your ISP, the ISP will provide a CSU that splits the
connection into separate voice and data elements. An Inter-Tel 3000 CO
Module can be connected to analog ports on the CSU using loop start for
voice connection.
3
Inter-Tel 3000 T1 Training Self-Study Course
4
Inter-Tel 3000 T1 Training Self-Study Course
Understanding ISDN, T1, and PRI
This section will provide the basic knowledge for installing and maintaining the
central office services of T1 and Primary Rate Interface (PRI).
Although the T1/PRI information contained here is applicable to any T1/PRI
service, this document specifically addresses T1/PRI and their implementation in
the Inter-Tel 3000 system. The Inter-Tel 3000 system requires at least version
3.0 system software and the installation of the Inter-Tel 3000 T1/PRI Module to
support T1/PRI service. Please refer to the applicable Inter-Tel 3000 manual(s)
for further information regarding the proper configuration of components, and for
information on wiring and physical installation.
T1 Overview
A typical T-carrier system consists of a transmission component, a user interface,
and termination equipment, as well as multiplexing schemes and signal
hierarchies.
Termination
Equipment
Channel
Service
Unit
Digital
Transmission
Media
Channel
Service
Unit
Termination
Equipment
Copper
Coaxial
Fiber
Microwave
Radio
Channel Bank
T1 Multiplexer
Transcoder
Digital Cross-Connect System
Termination Equipment
Several types of terminal equipment other than the basic switch provide digital
connectivity. The equipment can be grouped into three general categories:
•
Terminals (channel banks and transcoders): Terminals take analog
input and transform it into a digital stream.
•
Digital Cross-Connect Systems (DCSs): Digital cross-connects are the
interconnection points for terminals, multiplexers, and transmission
facilities.
•
Multiplexers: Digital multiplexers and transcoders are the interfaces
between the different bit rates in the digital network. They “stack” blocks
of data on top of each other before they enter a high-capacity
transmission media.
5
Inter-Tel 3000 T1 Training Self-Study Course
Channel Banks
A channel bank performs the first stop of call handling. Channel banks are a
bridge between the analog and digital worlds, and have two basic functions.
•
They convert analog voice to digital code, and digital code to analog
voice.
•
They combine, or multiplex, the resulting digital streams from several
active sessions (voice or data) onto a single stream. They are a
combination of the digital terminals and the digital multiplex function.
A channel bank is a Time Division Multiplexer used in T1 networks, which also
includes the CODECS (Coders/Decoders) for each channel. The channel bank
accepts 24 analog voice connections, digitizes the signals, and combines them
into a 1,544,000 bps T1 aggregate called a DS1, or digital signal level 1.
The CODEC samples each analog voice signal 8,000 times per second and
produces an eight-bit digital representation of each sample called Pulse Code
Modulation (PCM. The result is a 64,000 bps stream of digital signals called a
DS0, or digital signal level zero.
Time Division Multiplexer
CODEC
24
T1 Digital
Link
24
Aggregate
1.544
Mbps
CODEC
Analo
g
Analog
64 Kbps DIGITAL
CHANNELS
1
2
3
4
Chan 1
Chan 2
Chan 3
5
Aggregate
24
Time Division Multiplexer
6
Chan 4
Inter-Tel 3000 T1 Training Self-Study Course
A Time Division Multiplexer (TDM) divides the T-carrier into equal time slices,
and assigns one time slot to each channel. The TDM takes the information from
each channel, in sequence, and places it into a time slot on the T-carrier. Another
TDM at the other end of the link receives the aggregate stream and sorts it out
into the original channels.
The T1 multiplexer consists of fundamental elements:
•
Channel Interface Units (CSUs): These ports provide the physical level
connection of equipment, either voice or data, to the T1 multiplexer.
Channel interface units are available for synchronous data and
asynchronous data using several types of interfaces or connectors.
•
Buffer: There is a bulk data memory in the T1 multiplexer. It provides
data bit storage that can be read and written between the channels and
the aggregate Time Division Multiplexed link.
•
Frame Builder/Multiplexer: The frame builder, sometimes called the
Time Slot Interchanger (TSI), multiplexes the information from the
channel interface units into an aggregate for transmission over the T1
link. It also demultiplexes the received aggregate into separate channels.
The most common framing format is D4 format. This module usually is
referred to as a T1 Garage Card.
•
T1 Line Interface: The primary function of the T1 line interface is to
convert the aggregate stream, from the frame builder/multiplexer, to a
format suitable for T1 transmission. This includes converting the signals
from unipolar to bipolar format, controlling link transmit and receive
functions, framing control, and ensuring sufficient ones density.
•
Other Elements: Other elements usually include a timing reference and
a controller module that sets up the configurations and routing tables on
user command. The controller module may be attached to a supervisory
terminal that can be located at the same site or at a remote site.
•
Full Duplex: T1 links always operate in full duplex mode, where data
traffic flows in both directions, as shown in the above point-to-point
multiplexer configuration.
7
Inter-Tel 3000 T1 Training Self-Study Course
Pulse Code Modulation
Current channel banks utilize a standard arrangement of channel assignments
called the D4 format. Each eight bits of PCM (Pulse Code Modulation) coded
information is inserted into a TDM (Time Division Multiplexing) time slot. The 24channel structure was carried forward from the analog FDM (Frequency Division
Multiplexing) multiplexers for compatibility. Channel banks that conform to the
standard are known as D4 Channel banks, or D-banks.
D-banks have equipment to provide proper voice frequency and signalization
interfaces to the central office. They also provide filters to limit the input
frequency (300 to 3000 Hz voice frequency), so that Pulse Code Modulation
techniques employing 8,000 samples per second provide consistent voice
reproductions, and provide a means for controlling the timing and
synchronization.
The DS1 (1,544,999 bps) D4 format is used to transmit 24 separate channels of
PCM voice or digital data. Each channel is transmitted 8 bits at a time. All 24
channels are grouped together to form a group of 192 bits (24 channels times 8
bits). For synchronization of both end span equipment, every group of 192 bits is
preceded by a framing bit (F-bit). Together, all 193 bits make up a FRAME.
D4 Frame
125 Microseconds
DS 1 Frame = Total of 193 bits transmitted every 125 Microseconds
1 Framing Bit
192 Bits – Free Form
8
Inter-Tel 3000 T1 Training Self-Study Course
D4 Frame
In the D4 format, 24 channels are transmitted with 8 bits per channel, plus one
framing bit for synchronization every 125 microseconds (one frame every 125
microseconds). This is repeated 8,000 times per second (1 second = 8,000 125microsecond intervals) to produce 1,544,000 total bps (193 bits x 8,000 times per
second = 1,544,000 bps).
D4 Frame
125 Microseconds
D4 Format = 8 Bits Per Channel x 24 Channels, + 1 Framing Bit = 193 Bits every 125 Microseconds
1 Framing
Bit
Channel 1
8 Bits
Channel 2
8 Bits
Channel 3
8 Bits
Channel 4
8 Bits
Channels 5 through 24
8 Bits per Channel
1 Time
Slot
There’s more to voice transmission than carrying conversations. When a caller
picks up the phone (goes off hook) the request for service must be carried to the
central office, or PBX. Likewise, a digitally multiplexed voice channel between
PBX’s must allow one side to seize the line, carry dial pulses or DTMF, respond
with a busy signal, etc. Collectively, these functions constitute signaling. The
presence of a specific signaling condition is coded and multiplexed.
PCM channel banks have a standard way to transmit signaling. A small portion of
the channel can be used for signaling with no apparent effect on voice quality. In
North America, the least significant bit in every sixth sample per voice channel is
devoted to signaling. This is referred to as “bit robbing.” These bit positions aren’t
available for voice or data transmission.
D4 Format
1 Second
D4 Format =8,000 Frames of 193 Bits each, transmitted every second = 1,544,000 bps
Frame 1
193 Bits
Frame 2
193 Bits
Frame 3
193 Bits
Frame 4
193 Bits
24 Channels of 8 Bits each = 193 Bits
(8 Bits = 1 PCM Sample)
9
Frame 5
193 Bits
Frames 6 through 8,000
193 Bits Per Frame
Inter-Tel 3000 T1 Training Self-Study Course
The existing worldwide standard for digital voice is Pulse Code Modulation
(PCM). The incoming analog signal, representing the loudness of a voice, is
sampled 8,000 times per second. The modulator uses the sample to create a
very narrow pulse whose voltage (height) is the same as the analog signal. The
height of the pulse is then converted to an 8-bit word representing the analog
input at the time of the sample. The two-step process converts an analog signal
to a digital stream of 64,000 bps (8 bits x 8,000 samples per second = 64,000
bps).
PCM Sampling
1 Second
PCM Sample = 8,000 Samples of 8 bits each/every second = 64,000 bps
PCM
Sample 1
8 Bits
Information
PCM
Sample 2
9 Bits
Information
PCM
Sample 3
8 Bits
Information
PCM
Sample 4
8 Bits
Information
PCM
Sample 5
8 Bits
Information
PCM Sample 6
7 Bits
Information
1 Signaling Bit
Of the 8,000 samples per second, 6,667 samples are 8-bits of information, 1,333
samples are 7 bits of information, and 1signaling bit (6,667 samples of 8 bits =
64,000 bits of information + 1,333 samples of 7 bits = 9,331 bits of information +
1,333 signaling bits = 64,000 bps).
Notice that 24 channels multiplied by 64,000 bps doesn’t equal the 1,544,000
bps speed of the T1 channel (24 x 64,000 = 1,536,000). The remaining 8,000 bps
are the framing bits, used by the channel bank for synchronization.
Synchronization keeps the multiplexers at each end of the link channel-locked
with each other so that what goes in at one end on a specific channel comes out
the same at the other end.
The “robbed bit” method puts control information in-band (signaling is carried
along the same circuit as the talk path), so an individual voice channel can be
switched easily. In meeting the framing requirement, 1 bit in 193 is provided by
the multiplexer, leaving 1,536,000 bps available to the customer for transmission
of voice and data.
NOTE: A T1 span uses in-band signaling. An ISDN Primary Rate Interface (PRI)
uses out-of-band signaling. The PRI consists of 23 B-Channels (Bearer or
Information) and 1 D-Channel (Digital or Signaling). The customer has access of
23 channels carrying 64,000 bits of information per second. The D-Channel is
used to carry signaling and control information at 64,000 bits of information per
second. The D-Channel is used to carry signaling and control information at
64,000 bps.
10
Inter-Tel 3000 T1 Training Self-Study Course
Ordering T1
Sample T1 order forms are included in the back of this book. When ordering T1
spans, you must specify the framing scheme to be used on the span. There are
two framing schemes available:
•
D4 Superframe
•
Extended Superframe.
D4 Superframe
A superframe is a repeating sequence of 12 frames and thus contains 12
framing/signal bits (the 193rd bit of each frame). One frame corresponds to 125
microseconds; one superframe is thus 1.5 milliseconds in duration. Each frame
contains one synchronization bit to allow the receiving equipment to decode,
demultiplex, and allocate the incoming bits to the appropriate channels.
Each superframe thus contains a 12-bit word, comprising individual bits from
each of the 12 frames. The framing bits are called BFf, and the signaling bits are
BFs. BFfs are the odd-numbered framing bits, and BFs are the even-numbered
bits. The 12-bit word is used for synchronization and for identifying frame
numbers 6 and 12, which contain channel-signaling bits.
Each frame contains a BFf or BFs framing/signaling bit on the 193rd position.
The channel bank will “rob” or “share” the 8th bit from the user data stream. For
five frames, bit 8 will contain voice bits. On the sixth, it will contain a signaling bit.
These combinations of bits allow the end-user termination equipment to carry out
its signaling protocol, which involves indicating such states as idle, busy, ringing,
no-ringing, loop open, etc.
D4 Superframe Format
Frame
1
Frame
2
Frame
3
Superframe
Frame
4
Frame
5
Chan 1
B1
B2
B3
Frame
7
Frame
8
Frame
9
Frame 12 With
Signaling
BFs
BF
Frame
6
B4
Chan 2
B5
B6
Chan 3
B7
Frame
10
BFt
Chan 22
Chan 23
Frame
11
Frame
12
Frame 12 With
Signaling
Chan 24
B8
Signalling Bit = “Robbed Bit”
Speech Bits
or
Data Bits
Frame 6 = A Bit, Frame 12 = B Bit
Framing Bit
The signaling channels are divided into an A and B
subchannel, with the A subchannel information sent
in the sixth frame, and the B subchannel signaling
sent in the twelfth frame of every superframe.
ON HOOK
Signaling Bits
A=0
B=0
OFF HOOK
Signaling Bits
A=1
B=1
11
Inter-Tel 3000 T1 Training Self-Study Course
Extended Superframe Format (ESF)
The Extended Superframe format is an extension of the D4 format that was
announced in 1981. As old AT&T equipment is replaced, new equipment
supporting the ESF is installed, and users are offered the ESF. In addition to
benefiting end users indirectly by offering a more reliable digital service, ESF
allows the use of the bandwidth to provide more advanced services. Unlike the
D4 Superframe, which requires 8,000 bps for housekeeping, ESF requires only
2,000 bps. This implies that the other 6,000 bps become available for other
service-related purposes. Among these services might be the user’s ability to
reconfigure their networks in real-time from a data terminal.
The ESF has 24 frames in its definition of a Superframe, but only six bits in its
framing pattern. Rather than re synchronize every 1.5 milliseconds in the regular
format, it only needs to re synchronize every 3 milliseconds.
Extended Superframe
3 Milliseconds
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Signaling Frames 6, 12, 18 & 24
Channels per Frame
Chan
1
Chan
2
Chan
3
Chan
22
B1
B2
Chan
23
B3
B4
Chan
24
B5
B6
B7
B8
Frame 6 = A Signal
Frame 12 = B Signal
Frame 18 = C Signal
Frame 24 = D Signal
Remember that the framing bits are the 193rd bit of each frame. Since the ESF
uses 24 frames, the framing bits are seen as a 24-bit word.
The framing bit positions of the extended superframe are partitioned for three
separate uses:
1. Six of the framing bits are used for frame synchronization.
2. Six of the framing bits are block-check bits and are used for cyclical
redundancy checking (CRC6).
3. The remaining 12 bits are data link (DL) bits and are used to provide a
4 Kbps data channel.
12
Inter-Tel 3000 T1 Training Self-Study Course
The CRC6 and the DL bits are features of the ESF that provide capabilities for
network maintenance of the circuits.
Framing Bit Summary
D
C1
D
0
D
C2
Frame Synchronization
6 Bits
D
0
D
C3
D
1
D
C4
Data Link Bits
12 Bits
D
0
D
C5
D
1
D
C6
D
1
Error
Checking
6 Bits
Using the Extended Superframe Format, 2,000 bits per second are framing bits.
The cyclical redundancy check (CRC) uses 2,000 bits per second and detects
approximately 98.4% of all single and multiple errors. The CRC-6 also provides
false-frame protection. The data link (also called the Embedded Operations
Channel) uses 4,000 bps for maintenance information, supervisory control, and
other future needs. The user has the benefit of using the 6,000 bits for network
maintenance and error checking not available with the D4 Superframe format, as
all 8,000 bps are required for framing and signaling.
13
Inter-Tel 3000 T1 Training Self-Study Course
Coding Methods
When ordering a T1 span, the user must specify the coding method to be used
on the span. There are two coding methods available:
•
Alternate Mark Inversion (AMI)
•
Bipolar 8th Zero Suppression (B8ZS)
In the early 1960s, considerable study was given to the choice of a coding
method for placing the information signal onto the transmission carrier. A bipolar
encoding scheme was selected to prepare the signal for direct application to a T1
copper facility. The choice of bipolar was largely determined by the
characteristics of the copper medium. In bipolar coding, alternating positive and
negative pulses represent one state (a binary 1). Absence of bipolar coding
pulses represents the other state (a binary 0).
T1 information is transmitted as positive and negative marks (ones) that
alternate. A logical 0 is coded as a “zero excursion.” This coding technique is
called bipolar return to zero, or Alternate Mark Inversion (AMI).
Bipolar Pulse Stream
Binary 1
Binary 1
Binary 0
Binary 0
+3 Volts
-3 Volts
In this example, the first binary one is +3 Volts. The second binary one is -3
Volts. The absence of any pulse on the line (0 Volts) represents two binary zeros.
14
Inter-Tel 3000 T1 Training Self-Study Course
Bipolar Encoding
Bipolar encoding was selected for T1 spans because it possesses the following
properties:
•
Clocking need not be absolutely perfect for the bit to be decoded, and the
sampling need not be done exactly at the maximum signal level (+3
Volts). Any time that voltage is present, a binary 1 is read, even if the
voltage is below the specified level (-3 Volts). If no energy is present, then
a 0 is read.
•
Any single-bit error can be detached, which is useful since copper
facilities are subject to a variety of natural (e.g. lightening) and
mechanical (induction motors, elevators, power lines, etc.) noises. With
bipolar inversion, the polarity of any pulse must be opposite to the polarity
of the preceding pulse. The pulse is normally 3 volts in absolute
amplitude. If an error occurs in a 1-bit position, thereby converting it to a
0, adjacent 1s will be of identical polarity that is easily detectable since it
violates the polarity rule. If an error occurs in a 0, converting it to a 1,
there will also be two consecutive 1s of identical polarity, which also
violates the polarity rule. These are called “bipolar violations,” or “BVP.”
•
Remote maintenance margin testing. At least 50% of the stream should
be 0s.
Bipolar Violations
Bipolar violations (BPV), as described above, are important in T1 transmission.
The main limitation of Alternate Mark Inversion (AMI) coding is the absence of
timing information when the message signal consists of a long sequence of
binary zeros. This can be overcome by imposing restrictions on the message
signal. In North America, this is referred to as the “ones density requirement” to
maintain synchronization at least 12.5% (one-eighth), on the average, must be
binary ones and there can be no more than 15 consecutive binary zeros.
15
Inter-Tel 3000 T1 Training Self-Study Course
Bipolar 8th Zero Suppression (B8ZS) Coding
Traditionally, in meeting the ones density requirement, a further 1 bit in 8 is
required to be permanently set to a one, leaving a maximum of 1,344,000 bps
available to the customer equipment. Recent introduction of B8ZS encoding
(bipolar with eight zero substitution) of the T1 data eliminates the requirement of
ones insertion, leaving 1,536,000 bps of “clear channel” available. Not all central
office equipment currently supports B8ZS coding.
Bipolar 8th Zero Suppression (B8Zs) is a zero code suppression scheme. The
ones density condition (12.5% [one-eighth] on the average must be 1’s and no
more than 15 consecutive zeros can occur) can be met using the B8ZS
algorithm. (B8ZS is a favorite of ISDN for provision of the Clear 64 service.) With
B8ZS, deliberate bipolar violations in the frame (192 bits of PCM plus one
framing bit) are substituted whenever eight consecutive zeros occur in the bit
stream from which the frame signal is derived.
Bipolar 8th Zero Suppression
Frame Signal without B8ZS Coding = Transmission of a Binary 1 and Eight Binary Zeros
1
0
0
0
0
0
0
0
0
Frame Signal with B8ZS Coding =Two Bipolar Violations Replace the String of 8 Zeros
1
0
0
0
1
1
0
1
1
The “Bipolar 8th Zero Suppression” figure above illustrates the impact of B8ZS
coding. The top portion of the diagram shows the coded output of a channel bank
without B8ZS. The bottom portion of the diagram shows the effect of B8ZS - two
bipolar violations (two contiguous pulses of the same voltage polarity) are
deliberately inserted, replacing the string of eight zeros. The specific pattern
described is recognized as a legal indication of eight successive zeros and is not
a bipolar violation.
16
Inter-Tel 3000 T1 Training Self-Study Course
Channel Service Unit
So far we’ve talked about the terminal equipment, the channel bank, the framing
format, D4 Superframe or Extended Superframe, and the coding scheme,
Alternate Mark Inversion or B8Zs. There is another key piece of CPE supplied by
the user - the Channel Service Unit.
Termination
Equipment
Digital
Transmission
Media
Channel
Service
Unit
Channel
Service
Unit
Termination
Equipment
Copper
Coaxial
Fiber
Microwave Radio
Channel Bank
T1 Multiplexer
Transcoder
Digital Cross-Connect System
The Channel Service Unit (CSU) interfaces the transmission facility (T1 span) to
the user’s termination equipment (channel bank, T1 multiplexer, a digital crossconnect system, or a PBX). In digital transmission, precise synchronization is
essential, and the CSU is a key element of this synchronization process.
Basically, the CSU ensures a high-quality digital signal is sustained into and out
of the network.
The CSU can transmit and receive. In transmit mode, the device regenerates the
digital signal received from the user’s equipment, checks for bit stream errors,
and applies the regenerated signal to the transmission facility (T1 span). In
receive mode, the CSU regenerates the signal received from the network, checks
for remote loop back codes, and applies the signal to the customer’s equipment.
The FCC Rules, Part 68, require the CSU to provide certain network functions. In
the event of termination equipment failure, the CSU must send a continuous
stream of one pulses, called “Network Keep Alive,” to the T1 span and central
office.
T1 Data
Repeater
T1 Data
CPE
Channel Service
Unit
17
C.O.
Inter-Tel 3000 T1 Training Self-Study Course
Typically, CSUs are transparent to the data stream, but they must provide a
ones-density monitor that will force the mandated ones density requirement
(12.5% on the average must be binary ones) onto the data stream if it does not
comply. Unfortunately, it doesn’t recover the inserted ones at the far end,
implying data errors if the customer data stream doesn’t meet the ones density
requirement. The network was designed for voice traffic where occasional data
bit errors by random ones insertion are inaudible.
T1 network performance is optimized when facilities exist to detect and isolate
line and equipment problems. In-band and out-of-band signals at the network
interface enable maintenance personnel to conduct local and remote span
diagnostics. Front-panel switches on the CSU enable users to generate line-loop
back and test-loop back signals to diagnose local equipment problems. (Loop
back is the return of information back to the source at any one of a number of
locations in the network.) The CSU occupies a critical position in the network and
is used to aid in the detection and isolation of problems.
Channel
Service
Unit
Repeater
Central
Office
Digital Loop Back
Some of the tests performed by a CSU interrupt normal operations. Loop back
tests, for example, affect service. More sophisticated CSUs can monitor
performance of the T1 link on a real-time basis, and concurrently support traffic.
These CSUs can also activate alarms based on selectable thresholds and report
them to a central location. Some of the faulty conditions reported by a CSU are
signal level, all “1s” condition, loss of synchronization, framing error, bipolar
violation, jitter, bit error and errored seconds rate.
Channel Services Units can store and display facility performance parameters,
including errored seconds, failed seconds, and bit error rate. If properly
engineered, the CSU can provide conversion between D4 alternate mark
inversion and ESF signals, thus allowing end users to retain the existing
equipment while taking advantage of the monitoring features available with ESF.
18
Inter-Tel 3000 T1 Training Self-Study Course
Repeaters
The next point in the network is the repeater. When a signal is transmitted down
a cable pair, it is attenuated (loses strength) and distorted (noise is introduced)
by the characteristics of the cable. However, in digital transmission, the signal
intelligence is defined by the presence or absence of pulses, not by the shape as
in an analog carrier. Since the repeaters detect the presence or absence of
pulses and restore them to their original form and amplitude (height), the signal
arrives at the far end as a nearly exact replica of the transmitted signal. Since
noise and distortion are removed from the signal each time it is restored
(regenerated), the signal can be transmitted over long distances and arrive at its
destination in a zero-loss state.
Customer
Premise
Central
Office
Last
Line
Repeater
CSU
3,000 Ft.
Maximum
^^^^
^^^^
Repeater
1 Mile
Maximum
Repeater
^^^^
^^^^
Up to 40
Repeaters
Last
Line
Repeater
1 Mile
Maximum
Office
Repeater
3,000 Ft.
Maximum
Fault Locate Pair
T1 Data
Maintenance
Order Wire
The T1 span will typically have many repeaters up to a practical maximum of 40,
and they are separated by distances which are determined primarily by the cable
attenuation (signal loss) and the ability of the repeaters to filter out pulse jitter
(timing loss).
19
Inter-Tel 3000 T1 Training Self-Study Course
Regenerative Repeaters
Repeaters for digital signals are called “regenerative repeaters” since they create
brand new pulses to send along the line. The repeaters examine each incoming
“smeared” pulse and decide whether the pulse is binary one or zero. Based on
the decision made, either a brand new one or zero is created and sent along the
line. Noise or other impairments are not amplified and also sent along as with
analog transmissions. Repeaters are usually placed about one mile apart to be
able to reliably regenerate the 1,544,000 pulses per second.
New Pulse Starts Out
Regenerated Signal
Repeater
Pulse Travels Over Cable
Pulse Gets “Smeared”
Independent transmit and receive paths are provided to and from the central
office, using four wires (two for transmission in each direction). The repeaters are
bi-directional. Historically, the central office has provided power for the span
repeaters. This is slowly changing as fiber optics are being implemented. Fiber
cables cannot carry the power.
T1 Data
T1 Span
Repeater
T1 Data
Office
Repeater
Central Office
Switch
Control
Office Repeater
The T1 span is terminated at the central office with an Office Repeater (OR). The
OR regenerates the signal for routing and switching within the central office. The
office repeater ensures that the T1 data stream complies with 1.544 Mbps pulse
shape requirements, as defined in AT&T Publication 62411. This publication also
defines the ones density and framing requirements. The OR incorporates
circuitry to enforce ones density and detect bipolar violations.
20
Inter-Tel 3000 T1 Training Self-Study Course
Network Timing
T1 networks are designed to be synchronous networks. That is, data clocked in
at one point in the network has a fixed timing relationship to the point in the
network at which the data is clocked out. This means that the speeds at both
points are the same, and there is always a fixed frequency relationship between
clocks that transmit and receive the data. This is usually referred to as “frequency
locked.”
The North American T1 network is derived from a series of network multiplexer
unsynchronized clocks using a technique called “pulse suffering” to overcome
clock inaccuracies and fluctuation. However, this does not eliminate network
synchronization at the T1 level. Synchronization of the network at the T1 level is
achieved by framing (D4 or ESF in North America) the data streams and
frequency locking the node and network clocks. Loss of synchronization results
in “frame slips.” A frame slip is a condition in which framing is momentarily lost,
as well as network information, generally resulting in data loss.
There are a number of ways to synchronize a digital network consisting of TDM
nodes and T1 transmission links:
•
Plesiochronous
•
Network master clocking
•
Master-slave clocking
•
Network-wide pulse stuffing
In a T1 network, the bipolar pulse transmission technique is used because
clocking information is embedded in the data. Each pulse must last at least 50%
of the clock interval. There are 1,544,000 clock intervals per second, 650
nanoseconds each. Any delays in the pulse stream result in equal delays of the
clock and data. During transmission, clock and data are essentially locked
together so distribution of the T1 aggregate links provides a source of network
timing transmission.
Plesiochronous
A plesiochronous (pronounced please-e-ock-ronus) doesn’t synchronize the
network but uses highly accurate clock at each node so the slip rate between
nodes is acceptably low. These clocks are very expensive and would be needed
at every node. This method was not chosen for implementation in North America.
Network Master Clocking
This method involves selecting one node as the master clock reference node.
The master clock is distributed to outlying nodes, enabling them to lock to the
common master reference. This is a simple technique, with the outlying nodes
operating in a loop-timed node. Reliability considerations are an issue because
failure of the master node results in loss of the entire network.
21
Inter-Tel 3000 T1 Training Self-Study Course
Master-Slave Clocking
The major consideration in configuring a network master synchronized network is
the need for reliable network transmission. The distributed nature of the network
topology can be used to distribute a master reference by way of the T1 links
themselves.
In this typical configuration, the network master reference frequency is
transmitted to selected slave nodes. These nodes synchronize their clocks to the
reference and pass on to lower level nodes the network timing by way of the T1
transmission links. The process of passing the reference downward from one
level to another is referenced as master-slave synchronization.
Master Clock
Reference Node
S
M
Slave Node
S
S
Slave Node
Slave Node
With master-slave synchronization, all nodes are either directly or indirectly
synchronized and all run at the same nominal clock frequency. If the master node
or one of the master node level 1 or level 2 links should fail, it’s necessary to
rearrange the network clocking hierarchy. It would be possible to lock levels 2
and 3 together as independent “timing islands” by assigning one of the level 2
branch nodes as the alternate network master.
22
Inter-Tel 3000 T1 Training Self-Study Course
Channel Pulse Stuffing
Another method to prevent frame slips is called “pulse stuffing,” or justification.
This method avoids both slips and the requirement for clock synchronization.
Pulse stuffing can be used at both the channel level to correct for data terminal
equipment timing differences and at the T1 level to overcome network timing
discrepancies.
Channel pulse stuffing uses a data channel between end points of a network that
runs at a slightly higher rate than the input channel speed. The data channel can
carry all input data plus some variable number of bits or “stuff bits.” These bits
are inserted to “pad” the input data stream to a higher rate. This technique is
used for T-3 and T-4 networks when the incoming lower level signals (T1s) are
not synchronized to each other. Pulse stuffing is usually used in satellite
applications where the T1 network operates on a timing source independent of
the attached channels.
Jitter and Timing Inaccuracies
No matter how stable the clocks are at both ends of a digital transmission
system, certain amounts of instability occur in the received signal. Typical causes
are path length changes, receiver nose and repeater regenerator inaccuracies.
There is a simple way of viewing hitter on a T1 circuit. Jitter implies that the start
and end times of the bit are not always exactly where they should be at the same
time. The signal actually jitters back and forth with respect to the rise and fall time
of the signal. This degradation is also called “phase jitter.”
Data Stream
(Clock Interval is 650 Nanoseconds)
Jitter
23
Inter-Tel 3000 T1 Training Self-Study Course
Testing Network Systems
As a corporation’s communications traffic is increasingly put through a small set
of separate and distinct facilities, the potential liability from either catastrophic
failure of the communications vehicle (termination equipment of lines) or from a
deterioration of the service due to a partial impairment of some of these facilities
increases. This raises the critical issue of testing and diagnostic procedures and
equipment that must be put in place by a user of the T1 facilities to monitor,
prevent, or resolve any problems.
In-service tests can be performed while the facility is carrying actual traffic data.
Service-disruptive testing, for example, loop-around and direct bit error rate
(BER) testing means that the link must be taken out of service.
In-Service Testing
The access tester is a basic type of testing equipment that provides access to the
individual channels and to the A/B signaling bits, and may also provide
monitoring for error performance, integrity checking, and bit-stream pattern
synthesis. Access testers are ideal for voice applications.
Noise and cross-talk can affect the bipolar signal to the point where a no-pulse
condition is interpreted as a pulse condition. The resulting bipolar violations can
be counted. When the BVP violation rate is high, it is generally indicative of some
inherent problem. An instrument that measures this data can be useful in
isolating the problem and is ideal for interLATA and intraLATA facilities, and less
useful for non-telco facilities.
Framing errors occur when the receiving equipment or a repeater is incapable of
recovering the clock. Excess zeros in the bit stream can cause the repeaters in
the network to shut down and put the facility out of service. Instrumentation
capable of detecting excess zeros can help prevent or resolve problems.
The T1 signal must satisfy certain defined electrical levels (+3/-3 Volts) at the
repeater, the CSU and the termination equipment. Signals exceeding the
specifications will cause cross-talk on other circuits (e.g. circuits going through
the same repeater). Low signals will have noise.
Jitter occurs when timing doesn’t meet the specification of within 50 parts per
million. Jitter implies timing slips and data errors. Jitter control and the capability
of the various T1 components to tolerate the hitter are important in establishing a
reliable network. Jitter measurement is a sophisticated and fairly technical inservice test, and some detailed knowledge of the various jitter specifications is
required.
All-ones signal patterns are transmitted to keep the repeaters synchronized even
when no real data is being transmitted. Detection of this alarm condition will
indicate a failure of some network component.
The ESF format allows more sophisticated in-service tests to be carried out.
Some of the newer tests are based on a cyclical redundancy check (CRC) code
embedded in the bit stream formed by the accumulation of the 193rd bit. The
CRC can provide measurement of the line’s quality.
24
Inter-Tel 3000 T1 Training Self-Study Course
Service-Disruptive Testing
There are times when out-of-service testing is the only recourse available. These
types of tests may involve test equipment at each end, or an instrument
connected through a loop-around arrangement. In-service testing will detect only
50% of the signal errors. Two methods are used for this type of testing. The first
involves accessing the CRC data provided by ESF. The second method involves
out-of-service bit error rate (BER) testing.
25
Inter-Tel 3000 T1 Training Self-Study Course
T1 Networks
T1 networks have evolved considerably over recent years. Advances in
technology have improved efficiency, flexibility and reliability. Software control of
the equipment has enabled many complex and tedious functions to be
automated. Network management software can monitor the network and take
corrective action when problems occur, sometimes without the users even being
aware of the problem.
Advances within the network have enabled new services to be offered to meet a
wide variety of applications and reduce communications costs. In this section we
will discuss the most commonly used T1 network topologies.
Point-to-Point T1 Networks
The most basic form of T1 network is the point-to-point link. One T1 multiplexer is
at point A, a single 1.544 Mbps communications link, and another T1 multiplexer
is at point B. The channels, or ports, can be connected in any combination to
voice, data, facsimile, or video applications, based on he capability of the
termination equipment.
Fax
Voice
^^^
^^^
T1 Multiplexer
Chandler, AZ
T1 Link
1.544 Mbps
T1 Multiplexer
Phoenix Branch
64 KBps
Channels
^^^
^^^
Host
26
Inter-Tel 3000 T1 Training Self-Study Course
Point-to-Point Multiple Links
Point-to-point applications can also operate with multiple T1 links. Multiplexers
with more than one link can operate in several ways. One link may be used as
the primary link, and the second as a backup. If the primary fails, the multiplexer
will automatically switch to the backup.
Multiple aggregate multiplexers are the functional equivalent of two or more
multiplexers in one cabinet, to provide additional capacity. The links are
sometimes set up in a “load sharing” configuration, where the traffic is routed
over both links more or less equally. This arrangement also provides an
automatic backup for when one link fails; all traffic is sent over the remaining
operational links. The links are usually routed to the distant location over different
paths to avoid common points of failure. This is called “diverse routing.” The
carriers can do this quite easily for the long haul network, but the local loops from
the customer premise to the central office are more difficult to diversify.
Fax
Voice
^^^
^^^
Printer
^^^
^^^
Multiple
Aggregate T1
Multiplexer
Chandler, AZ
T1 Link 1.544 Mbps
Multiple
Aggregate T1
Multiplexer
Phoenix Branch
64 KBps
Channels
T1 Link 1.544 Mbps
PC
Host
27
Inter-Tel 3000 T1 Training Self-Study Course
Point-to-Multipoint Networks
When the full 24-channel capacity of a T1 link is not needed at some of the
remote locations, a point-to-multipoint network can be the most cost effective
configuration. These networks are similar to multidrop or multipoint links used in
analog modem networks. The T1 links are routed from point A to point B, from B
to C, and so on.
Channels
A to B
T1 Link
B to C
T1 Link
Point A
24
Point B
Point C
Channels 13-24
Channels 1-12
The multiplexer at point B must be able to selectively remove and insert traffic
from the appropriate channels (drop and insert) and pass the remainder along to
point C (bypass). Individual channels are demultiplexed at a local port in the
multiplexer and patched, via cable, to a port on a second multiplexer. (This
channel bypass is not the same thing as bypassing the local telephone company
to reach a long distance carrier.)
Insert
T1
CSU
Point B
CSU
Point C
T1
Point A
CSU
CSU
Point B
Channels “Dropped”
at Destination B
Drop and insert has some drawbacks that become more serious as network size
increases. The cost and complexity of input/output ports and cables increase,
space and power requirements grow, control and management get more difficult
and conversion from digital to analog and back to digital adds quantizing noises
to voice channels.
Channel bypass handles the routing of channels from destination A to
destinations B and C somewhat differently. Channels earmarked for B are
demultiplexed at the B-site multiplexer, while channels destined for C bypass the
demultiplexing function at site B and are routed directly to destination C.
28
Inter-Tel 3000 T1 Training Self-Study Course
Star Networks
When many point-to-point links terminate at a central location, the network is
called a star network. The multiplexers may be single aggregate or multiple
aggregate, but they are all operating on simple point-to-point links. The star
topology is one of the most expensive in terms of line costs when long distances
to the remote locations are involved. When many point-to-point links terminate at
a central location, the network is called a star network.
Mesa
Central
Location
Phoenix
Scottsdale
Chandler
Tempe
Ring Networks
Multiple aggregate T1 multiplexers can also be arranged to form ring networks.
The ring topology provides “built-in” link redundancy. When one T1 link fails in
the ring, the traffic can be rerouted around the ring in the reverse direction and
still get to the destination. Ring networks also utilize the drop and insert and
bypass features to remove and place traffic onto the network.
Dual Aggregate
T1 Multiplexer
T1 Link
T1 Link
Dual Aggregate
Dual Aggregate
T1 Multiplexer
T1 Multiplexer
T1 Link
T1 Link
Dual Aggregate
T1 Multiplexer
29
Inter-Tel 3000 T1 Training Self-Study Course
Mesh Networks
Mesh networks are similar to ring networks, but have additional T1 links to
interconnect each T1 multiplexer directly with every other multiplexer. The mesh
topology is the ultimate in redundancy and offers the added benefit of minimum
transmit time for information to flow through the network. This is done to ensure
the connection is given the shortest available path as network loading changes.
Dual Aggregate
T1 Multiplexer
T1 Link
T1 Link
T1 Link
Dual Aggregate
Dual Aggregate
T1 Link
T1 Multiplexer
T1 Multiplexer
T1 Link
T1 Link
Dual Aggregate
T1 Multiplexer
30
Inter-Tel 3000 T1 Training Self-Study Course
T1 Services
The companies offering long distance T1 services are called Interexchange
Carriers (IEC or IXC) as they provide service between central office exchanges.
•
Local T1 services are provided by the Local Exchange Carrier (LEC). The
most common LECs are the Regional Bell Operating Companies
(RBOCs).
•
T1 services are also available from the domestic satellite carriers
(DOMSAT) that include AT&T, American Satellite, SGS, GTE, Spacenet
and RCA Americom.
LATAs
As part of deregulation, the United States was divided into geographical areas
called Local Access and Transport Areas (LATAs). The local telephone
company, which can be an RBOC or an independent, provides service only
within the LATA. The service can be an end-to-end link if both ends are within the
LATA. They also provide the portion of the link from the customer’s premise to
the interexchange carrier point-of-presence (POP) for service between LATAs.
The interexchange carriers such as AT&T and Sprint, as well as other long
distance carriers for long-haul circuits provide inter-LATA service. The RBOC can
also provide inter-LATA service if the LATAs are within the RBOC serving area.
For example, a Miami, FL to Jacksonville, FL link crosses several LATA
boundaries, but all are within Southern Bell operating territory.
The interexchange carrier will generally take the responsibility for coordinating
the ordering, installation and maintenance between the LEC and IXC, and
provide billing for the entire link.
LATA 1
POP
Customer
CO
CO
Interexchange
Carrier
CO
LATA 2
Customer
POP
CO
31
Inter-Tel 3000 T1 Training Self-Study Course
Method of Access
The method of access determines the cost per minute for long distance services.
There are two methods for accessing the interexchange carrier - switched access
and dedicated access.
Switched Access
The access is “switched” when the local operating company (local exchange
carrier) routes the long distance access to the interexchange carrier, through the
central office on a call-by-call basis.
Business
Line Monthly
Rate
1
0
X
X
X
Long
Distance
Carrier
Central
Office
Local Exchange
Carrier Computer
Switched
The local exchange carrier charges for switching the call through the local central
office. This carrier access charge (CAC) is billed per minute on each long
distance call routed through the central office to the interexchange carrier.
Dedicated Access
Dedicated access eliminates the switching through the central office and
eliminates the CAC per minute charged by the local exchange carrier.
Central
Office
Long
Distance
Carrier
T1 Link
Local Exchange
Carrier Dedicated
Access
Dedicated access costs less per minute since the CAC is eliminated. However,
dedicated access requires a volume of lines to justify the monthly rate for the T1
circuit. NetSolutions recommends that customers who spend between $3,500.00
and $4,000.00 per month in switched long distance will be at the break-even
point for dedicated T1 access.
Dedicated vs. Switched Access
With switched access, when the customer picks up the phone and dials a long
distance number, the LEC takes the call and sends it to the long distance carrier.
They “switch” the call. The long distance company is charged a percentage for
switching the call and that charge is built into the cost per minute to the user.
32
Inter-Tel 3000 T1 Training Self-Study Course
Benefits of T1 Access
With T1 access, the customer dials a long distance number and the call goes
directly to the long distance company. The user is charged a flat monthly rate for
access. Since the LEC is not switching the calls, that percentage is dropped from
the price of the call charged to the user. If the calling volume warrants paying the
monthly access charge, the user can save on long distance calls. NetSolutions
has found that $3,500.00 a month in long distance is an average break-even
point.
The user also benefits with T1 access because the call set-up time is shortened.
The user is flagged as a priority customer because they are directly connected to
the carrier. With T1 being totally digital, the calls are clearer and user data has
better protection. The user has the latest technology right to his doorstep. Digital
allows the customer to use features like special routing for 800 numbers, Dialed
Number Identification Service (DNIS) and real-time Automatic Number
Identification (ANI).
Configurations and lines can be changed quickly. Unused lines can be “turned
up” very quickly. T1 spans are easier to troubleshoot than analog lines.
Dedicated access allows the long distance carrier to troubleshoot the entire
network. Most newer T1 multiplexers are software configurable. Through a
terminal, the user can add or delete channels, change configurations, initiate
diagnostic tests, monitor network performance, and check the operating status of
remote units from a central location.
Many software-based multiplexers offer additional flexibility, such as the ability to
assign priority to channels or automatically reconfigure the system at
predetermined times to accommodate different traffic patterns.
Fractional T1 Service
Fractional T1 (FT1) service provides users with cost-efficient alternatives to some
of the older private line services (e.g. analog private lines, digital data service,
and full T1 circuits).
FT1 service is most attractive to low-to-medium volume users. It benefits small
organizations requiring more bandwidth than is provided by standard private line
digital service offerings, but do not need or cannot afford full T1 links. FT1 might
prove to be most beneficial to users who are geographically confined, such as
branch banks, state governments and universities.
33
Inter-Tel 3000 T1 Training Self-Study Course
ISDN Overview
Integrated Services Digital Network (ISDN) is a worldwide standard for
transporting information digitally across the public switched telephone network. It
defines a structure for the network and incorporates flexibility to include new
technologies and services as they are developed.
ISDN voice and data are carried by bearer channels (B channels) that use a
bandwidth of 64 kb/s (bits per second). A data channel (D channel) handles
signaling at 16 kb/s or 64 kb/s, depending on the service type.
There are two basic types of ISDN service:
•
Basic Rate Interface (BRI): BRI consists of two 64 kb/s B channels and
one 16 kb/s D channel for a total of 144 kb/s. This basic service is
intended to meet the needs of most individual users. (This is not currently
supported by the Inter-Tel 3000.)
•
Primary Rate Interface (PRI): PRI is intended for users with greater
capacity requirements. Typically the channel structure is 23 B channels
plus one 64 kb/s D channel for a total of 1536 kb/s. In Europe, PRI
consists of 30 B channels plus one 64 kb/s D channel for a total of 1984
kb/s. It is also possible to support multiple PRI lines with one 64 kb/s D
channel using Non-Facility Associated Signaling (NFAS).
There are three primary local ISDN services:
•
ISDN Centrex: Support for BRI Services as part of a digital Centrex
offering. ISDN Centrex can also be configured with PRI access to
Interchange Carriers (IXCs) if required.
•
ISDN Single Line Service: ISDN single line service is essentially BRI
service for either business or residential customers. The targets for this
service are business customers who need some of the ISDN capabilities
(e.g. ISDN BRI for video teleconferencing and work-at-home
applications).
•
ISDN Primary Rate Service: ISDN Primary Rate Service provides
connection to the local ISDN for PBX, ACD, and Calling Line Identification
features.
34
Inter-Tel 3000 T1 Training Self-Study Course
Primary Rate Interface (PRI)
PRI is intended for multi-user systems like PBXs, Automatic Call Distributors
(ACDs), or higher bit rate terminals. The 23 B channels available can support a
mix of voice and data connections.
High bit rate services can be provided over a PRI by grouping multiple B channel
connections to form 384K and 1536 kbps channels.
In the United States, the PRI has two configurations:
•
23 B + D (64 kbps)
•
24 B (24B is only available with a service called “Non-Facility Associated
Signaling” (NFAS) using “D channel backup,” which allows control
signaling on a D channel equipped on another PRI span. This
configuration is not available on the Inter-Tel 3000 system).
PRI operates at the standard North American DS-1 transmission rate (1.544
mbps) and uses the same transmission specification as a T1 Carrier Span. The
transmission channel must support Extended Superframe Format (ESF) and
Bipolar 8 Zero Substitution (B8ZS).
The PRI can operate on any digital transmission system supporting DS-1.
PRI can be carried on:
•
T-Span (2 copper pairs with repeaters)
•
DS-1 Channel provided on a digital microwave
•
DS-1 Channel provided on a fiber optic system
•
DS-1 Channel provided on a SONET system
35
Inter-Tel 3000 T1 Training Self-Study Course
ISDN Hardware Definitions
•
Terminal Equipment 1 (TE1): This is an end-user type of device directly
compatible with BRI or PRI. Examples include ISDN compatible
telephones, fax machines and P C cards.
•
Terminal Equipment 2 (TE2): Analog devices that don’t support an ISDN
interface. Examples include Single line telephones, keysets, RS-232
devices, modems, two-wire analog (Tip and Ring) service, RS-232/RS449 and V.24/V.35.
•
Terminal Adapter (TA): A device used to connect an ISDN network to a
non-ISDN (TE2) compatible device
•
Network Termination 1 (NT1): This is a customer-provided hardware
device on the customer’s premise that connects to the local telephone
company’s loop facility. The NT 1 for PRI is the same Channel Service
Unit (CSU) currently used for T1/DS-1 rate services. The NT1 functions
to:
•
o
Isolate the customer equipment from the network
o
Provide four-to-two-wire conversion for BRI
o
Facilitate interface sharing (BRI passive bus)
o
Allow maintenance testing
o
Provide power for the downstream (customer side) equipment
Network Termination 2 (NT2): A device used to connect ISDN and nonISDN devices to an ISDN interface. Examples include: PBX Systems,
Automatic Call Distributors (ACDs), Terminal Controllers and Gateways.
TE1
TE2
(I.e. ISDN phone)
(I.e. a PC)
NT1
CO
TE2
(I.e. a FAX machine)
TA
(Terminal Adapter:
Converts TE2
Device to work
On ISDN line)
R Interface
S/T Interface
36
U Interface
Inter-Tel 3000 T1 Training Self-Study Course
ISDN Reference Points
The ISDN reference points are junctions at which two ISDN compatible devices
are connected. The 5 main reference points are explained below.
•
R Reference Point: This is the connection between a non-ISDN terminal
(PC w/modem, fax, credit card reader, etc.) and a Terminal Adapter (TA).
•
S Reference Point: This is the connection between Terminal Equipment
1 (TE1) or a Terminal Adapter (TA) and a Network Termination 2 (NT2).
•
T Reference Point: This is the connection between the Network
Termination 1 (NT1) and the ISDN Terminal (TE1).
•
U Reference Point: The connection between the Network Termination 1
(NT1) and the telephone company’s line, normally referred to as the
“demarc,” or “demarcation point.”
•
R Reference Point: This is the connection between a non-ISDN terminal
(PC w/modem, fax, credit card reader, etc.) and a Terminal Adapter (TA).
•
V Reference Point: This is the connection in the central office between
the ISDN line card and the line termination. The V reference point is
inside the central office and in most cases, is of no concern to the
customer.
TE1
TE2
(I.e. ISDN phone)
(I.e. a PC)
NT1
CO
TE2
(I.e. a FAX machine)
TA
(Terminal Adapter:
Converts TE2
Device to work
On ISDN line)
R Interface
S/T Interface
37
U Interface
Inter-Tel 3000 T1 Training Self-Study Course
D Channel Signaling
For both PRI, the D channel controls the activity on the B channels. The D
channel is a dedicated communication link between the Central Office and the
customer site equipment.
The protocol for ISDN D channel signaling is designed in a layered format to
provide flexibility in the design. This feature facilitates the incorporation of
enhancements to ISDN services without redesigning the signaling protocol
D channel signaling is established and interpreted using the Open Systems
Interconnection (OSI) Reference Model. This model defines protocols for
communication between systems, allowing systems made by different
manufacturers to communicate and providing an open network where any ISDN
device can communicate with any other device.
The OSI Reference Model defines seven protocol layers. These layers do not
necessarily define physical equipment. The standard representation of the OSI
Reference Model is shown below. The entire group of protocols is called a
“stack.” The function of each layer is described below.
LAYER
FUNCTION
DESCRIPTION
Layer 7
Application
Provides functions for particular services such as file
transfers, virtual terminals, etc.
Layer 6
Presentation
Used to specify format and coding, including encryption
if necessary, of communication packets from the
Application Layer.
Layer 5
Session
Allows the presentation packets (see Layer 6) to
organize and synchronize their data exchange.
Layer 4
Transport
Is responsible for connection between the end points of
the systems.
Layer 3
Network
Is for routing data, including network addressing,
routing, switching, acknowledgments, etc. This layer is
responsible for decoding the address of the message,
providing error recovery for incorrect addressing, and
determining the message destination.
Layer 2
Data Link
Defines formats for data transmission.
Layer 1
Physical
Defines the mechanical and electrical signaling
standards for data transmission.
Although setting up an ISDN call doesn’t require a thorough knowledge of the
workings of each of the layers, it is helpful to have an understanding of what
occurs in each.
38
Inter-Tel 3000 T1 Training Self-Study Course
A model of computer-to-computer connection would look something like this:
Layer 7
Application
Layer 7
Application
Layer 6
Presentation
Layer 6
Presentation
Layer 5
Session
Layer 5
Session
Layer 4
Transport
Layer 4
Transport
Layer 3
Network
Layer 3
Network
Layer 2
Data Link
Layer 2
Data Link
Layer 1
Physical
Layer 1
Physical
From the computer user’s perspective, things start at Layer 7 of one stack, “drop
down” through the layers, picking up information and formatting along the way.
Then, they’re transmitted across some medium (fiber, telephone cable, radio
waves, etc.) and finally filter up through the layers at the other stack “losing”
formatting as they go.
For example, let’s assume a single terminal-to-terminal communication session,
a chat room on an Internet connection. You type “Hello” on your computer, and
it’s seen on your friend’s screen. You’re typing is at Layer 7, the Application
layer. The letters you type become data to be sent out.
•
The data is sent (internal to the computer - you haven’t gotten to the
transmission medium yet) to the Presentation layer - Layer 6 - where
communications services mask differences between various data formats.
In addition, this layer is concerned with security and would apply
encryption if necessary. A header is added to the data from Layer 7. This
is added to the beginning of the data from Layer 7.
•
This new data stream is sent to the Sessions Layer. At this layer, the
communications facility provided by the previous layer is controlled.
Communications links are built up/torn down. This header is added to the
beginning of the data from Layer 6 (which, remember, contains the data
from Layer 7).
•
The constantly growing data string is sent to the Transport Layer. Here,
the rules for information exchange and end-to-end delivery of information
are specified. Another header is added to the data from Layer 5 (which
contains Layer 7, Layer 6 and Layer 5’s information).
•
At this point, the data is sent to the Network Layer. This layer determines
how data is transferred between computers and individual networks. The
information for Layer 3 is added to the data from the previous layers.
•
Everything now goes to the Data Link Layer. This layer is concerned with
the procedures for operating the communications lines. In addition, error
checking and correction, as well as alarm generation, are performed at
this level. Also, data organization into frames is done at this layer. The
data from Layer 2, in the form of another header, is added to the data
from the other layers.
39
Inter-Tel 3000 T1 Training Self-Study Course
•
The entire batch of data is sent to the Physical Layer and is pumped out
over the transmission medium.
NOTE: The medium itself is not part of the OSI Model. The model
concerns itself with getting data to and from the transmission medium. As
such, it doesn’t matter whether the medium is a PRI line or a computercontrolled semaphore lamp.
•
The data is sent over the transmission medium to the receiving computer
where it goes up the stack (Layer 1 to Layer 7). AT each successive
layer, the information (header) needed for that layer’s functions is read,
acted upon, and stripped off. By the time the data is received by Layer7
(at the recipient), all that’s left is the data that left your application layer.
This is then handled by the application at the recipient, which, for our
example, displays the word “Hello” on the screen.
In ISDN calls, you will be most concerned with Layers 1, 2, and 3. Anything
above that is part of the phone system or Central Office switch software and not
under your control. You will find the use of a PRI test box will be invaluable to
troubleshooting problems with a PRI line if the tester has the ability to display the
Layer 3 messages. Layer 2 is mostly concerned with alarms, clock timing, etc. As
such, an error at this level will more likely result in a failure to connect the T1
circuitry.
40
Inter-Tel 3000 T1 Training Self-Study Course
Installing T1 on Inter-Tel 3000
The ISDN PRI service connects to the Inter-Tel 3000 system via an Inter-Tel
3000 T1/PRI Module.
The system supports one 24-channel T1 or one 23-channel PRI connection.
Supported Switch Types
Each PRI Trunk must be configured for the proper switch type (AT&T 5ESS, or
National ISDN 2) and type of service (dedicated service, switched call-by-call
access, or a combination of the two).
No other switch types are currently supported by the Inter-Tel 3000 system.
41
Inter-Tel 3000 T1 Training Self-Study Course
System Installation Steps
To install an Inter-Tel 3000 with a T1/PRI Module, you will follow these steps:
1. Read the safety and precaution information in the manual carefully.
2. Plan the installation, including the CCU location, station locations, cable
runs, and optional equipment.
3. Mount the CCU as detailed in the manual.
4. Install as many CO line, T1, expansion, and extension modules as
required. The CO line, Voice and T1 module locations in the CCU are
indicated below.
T1Module
CO Module 1
CO Lines 1 and 2
CO Module 2
Voice Module
CO Lines 3
Installing the T1/PRI Module is very simple. Just open the CCU cover and
install the module in the proper location. NOTE: The T1/PRI Module can
be removed or inserted with the power turned on.
42
Inter-Tel 3000 T1 Training Self-Study Course
5. Replace the CCU cover.
6. Run cables to the phones and terminate the station cables on modular
jack assemblies at the station locations. T1 cabling depends on the type
of T1/PRI termination used by the telephone company (telco) and how
close it is to the CCU.
a. For T1/PRI trunks terminated on RJ48C jacks near the MDF, use
a four-pair, non-reversing, mod-to-mod line cord to connect the T1
to the CCU.
b. For T1/PRI trunks terminated on RJ48C jacks away from the CCU,
you will need two eight-conductor modular jacks and two four-pair,
non-reversing, mod-to-mod line cords. Run enough cable to
extend from the telco RJ48C jack to the CCU.
43
Inter-Tel 3000 T1 Training Self-Study Course
c. For T1/PRI trunks terminated on an RJ-type block, use an eightconductor modular jack assembly and a four-pair, non-reversing,
mod-to-mod line cord. Run enough cable to extend from each
telco termination to the CCU.
7. Connect the trunks, station cables, and circuit card cables to the CCU.
The T1 span is connected to the Inter-Tel 3000 CCU using an RJ45
connector.
8. Install the phones.
9. Power up the system.
10. Ensure that all equipment is working properly.
11. Use Administrator phone programming or the Maintenance and
Programming Software to configure and program the system.
44
Inter-Tel 3000 T1 Training Self-Study Course
Programming T1 on the Inter-Tel 3000
The programming necessary for establishing T1 services on the Inter-Tel 3000
can be performed using the Administrator’s phone or the Maintenance and
Programming software.
Using either method, here are the fields that need to be programmed:
When a T1 Module is installed, it is automatically set as a T1 interface with 24
E&M wink start channels. It can be changed to PRI ISDN.
T1 Channel Programming
The programming and set up options available on the T1/PRI interface are
described below.
T1 default settings are as follows:
•
Framing is set as D4 Superframe.
•
Coding is set as AMI.
•
Line Build-Out is set at -7.5dB.
•
The Line Type is E&M with no Service Types and Wink Start.
•
The received digits are set at 2.
•
The Line gain is set at -3dB.
•
Dialing is set at DTMF.
Each of these settings can be changed as required.
•
Framing Type: There are two different types of Framing provided by the
carrier that are programmable on the T1 interface. They are D4
Superframe or Extended Superframe. The default setting is D 4
Superframe.
•
Coding Type: There are two different types of coding programmable on
the T1 interface. They are either AMI or B8ZS. The default setting is AMI.
•
Line Build-Out: The Line Build out can be set at 0dB, -7.5dB, -15dB or 22dB. The default is -7.5 dB.
•
Line Type: The Line Type can be set as E&M (default), DID, Loop Start
or Ground Start. The default is that all lines are set as E&M.
45
Inter-Tel 3000 T1 Training Self-Study Course
•
Service Type: Once the line type is selected the Service Types relevant
to the particular type of line is presented. For E&M Line Type the
following Service Types are available:
o
None - No Service Type is set (default)
o
ANI
o
DNIS
o
*ANI*
o
*DNIS*
o
*ANI*DNIS*
For DID Line Types the following options are available: o
None - No Service Type is set (default)
o
ANI
o
DNIS
o
*ANI*
o
*DNIS*
o
*ANI*DNIS*
For Loop Start Line types the following options are available: o
None - No Service Type is set (default)
o
Caller ID.
If Ground Start is selected no additional menu is presented. There are no
services available on Ground Start lines.
•
Start Type: When E&M Service Type is selected four Start Types are
available:
o
Immediate.
o
Wink (default)
o
Delay Dial.
o
Dial Tone.
When DID Service Type is selected three Start Types are available.
o
Immediate.
o
Wink (default)
o
Dial Tone.
46
Inter-Tel 3000 T1 Training Self-Study Course
•
Received Digits: If Received Digits is selected the display updates to
show the equipped T1 lines. Up to 32 digits can be received between ANI
and DNIS. The default setting is 2 digits.
•
Line Gain: If Line Gain is selected the menu options are “Low”, “Medium”
or “High”. The default is that all lines are set to high -3dB. (Low is the
recommended receive setting as specified in EIA 464C. Medium is the
recommended value in EIA 464B.)
•
DTMF/Pulse Dialing: Either DTMF of Pulse Dialing can be selected for
the T1 channels. In default, all lines are set to DTMF dialing.
PRI Channel Programming
If PRI is programmed the default settings are as follows:
•
The ISDN Signaling Protocol (Q931) is set to National ISDN 2.
•
The Line Build Out is set to -7.5 dB.
•
The Line Gain is set to High at -3dB.
Each of these settings can be changed as required.
•
ISDN Signaling Protocol (Q931): Two ISDN signaling protocols are
supported, National ISDN 2 and AT&T 5ESS.
EXCHANGE EQUIPMENT (TELCO)
TRANSLATION PROTOCOL
INTER-TEL 3000 ISDN SWITCH TYPE
AT&T 5ESS (AT&T Custom)
AT&T 5ESS (Custom)
AT&T 4ESS (AT&T Custom)
AT&T 5ESS (Custom)
NORTEL CUSTOM (DMS Exchange)
NATIONAL ISDN 2
NATIONAL ISDN 1 (DMS Exchange)
NATIONAL ISDN 2
NATIONAL ISDN 2
NATIONAL ISDN 2
•
Line Build-Out: The Line Build-Out can be set at 0dB, -7.5dB, -15dB or 22dB. The default setting is -7.5 dB.
•
Line Gain: You can select either “Low”, “Medium” or “High”. The default
setting is High -3dB. (Low is the recommended receive setting as
specified in EIA 464C. Medium is the recommended value in EIA 464B.)
47
Inter-Tel 3000 T1 Training Self-Study Course
Line Programming for T1
When a T1/PRI module is equipped the following “Line Programming” options are
modified. The change is dependent on whether the interface is programmed as a
T1 or PRI interface.
Equipped Lines
•
For T1: In default, all 24 T1 lines are programmed as equipped. The line
numbers correspond to the T1 channels.
•
For PRI: The number of ISDN B-channels available is set in the Equipped
Line Programming. In this case lines 1-23 are the B-channels and Lines
24-27 are any CO lines installed. In the case of ISDN PRI there is no
direct correlation between the line number and any particular B-Channel.
Outgoing Groups
•
For T1: is programmed. Individual T1 channels. Up to 11 groups can be
set up, each with a corresponding access code, 9 or 760 - 769. In default,
all lines, T1 and backup are in group 1 selected by dialing 9.
•
For PRI: In this case, all available B-Channels must be programmed into
the same line group. In default, the PRI and CO Lines are all in Group 1,
selected by dialing 9.
All Other Line Programming
You can program the following line features, just as you would program them for
CO lines:
•
•
•
•
•
•
Incoming Ringing / Auto Attendant / Courtesy Service: Each T1/PRI
line can be programmed to ring a different group or extension. They can
be individually programmed to be answered by Auto Attendant or the
Courtesy Service in the normal manner.
Incoming Only: You can select the required lines to be reserved for
incoming calls only. In default, no lines are programmed. If 23 BChannels are available and 10 lines are selected, a total of 13 BChannels are available to extensions to select for outgoing calls. If a user
selects a Line key of a line that is set as Incoming only, busy tone is
returned and the message 'Restricted' is shown on the display.
Outgoing Restriction: You can select the extensions to be restricted
from selecting the line for outgoing calls.
LCR Codes: You can program the LCR codes for T1 or PRI, just as you
would for CO lines.
System Voice Mailbox: System Voice Mailbox Programming for T1 or
PRI is the same as for CO lines. You can select the lines to be answered
by the System Voice mailbox.
Calling Number Routing and Called Number Routing: Just as with the
CO lines, T1 and PRI calls can be routed to extensions or groups based
on Caller ID, ANI, DID or DNIS information received from the network.
48
Inter-Tel 3000 T1 Training Self-Study Course
Glossary of Terms
2B+D: A 2B+D circuit is divided into two 64 kbps B-channels that can carry
voice, video or data. It also has a 16 kbps D-channel for low-speed data and
signaling. There are two types of 2B+D interfaces that use different wiring: the
“U” interface uses a single twisted pair and the “S/T” interface uses two twisted
pairs. This is also referred to as “Basic Rate Interface (BRI).”
23B+D: A 23B+D circuit is divided into 23 B-channels (64 kbps each) that can
carry voice, data and video simultaneously. It also has a 64 kbps D-channel for
out-of-band signaling, call control, and packet data. This interface uses two
twisted-pairs of wire. This is also referred to a as “Primary Rate Interface (PRI).”
30B+D: This is the standard European ISDN interface. A 30B+D circuit is divided
into 30 B-channels *(64 kbps each) that can carry voice, data and video
simultaneously. It also has a 64 kbps D-channel for out-of-band signaling and call
control, and one framing channel. This interface uses two twisted-pairs of wire.
Alternate Mark Inversion (AMI): T1 information is transmitted as positive and
negative marks (ones), which alternate. A logical 0 is coded as a “zero
excursion.” This coding technique is called bipolar return to zero, or Alternate
Mark Inversion (AMI).
Automatic Call Number Identification (ANI): ANI information identifies the
caller’s telephone number. The system receives a specified number of digits.
*ANI* is another type of ANY that doesn’t require a specified number of digits.
The system receives a star (*) before the ANI digits to signal the beginning of the
caller’s telephone number. Another star signals the end of the ANI information.
B-Channel: The B-channel, or “bearer” channel, is the basic component of ISDN
interfaces. A B-channel can transmit or receive voice or data at up to 64,000 bps
(64kbps).
B-Channel Negotiation: This allows the Phone system to request the channel
that will be used for each call. When the Phone system requests a specific Bchannel for an outgoing call, the network decides which channel will be used.
Bandwidth: The bandwidth of a device determines the frequency range it can
handle. Different types of communications use different bandwidths. For
example, telephone communication requires a relatively narrow bandwidth, while
video requires a wide bandwidth.
Basic Rate Interface (BRI): Also called 2B+D, BRI provides two 64kbps Bchannels that can carry voice or data and a 16 kbps D-channel for low-speed
data and signaling. This can be used for homes and Centrex sites that do not
require PRI.
Bipolar 8th Zero Suppression (B8ZS): Bipolar 8th Zero Suppression (B8ZS) is
a zero code suppression scheme. The ones density condition (12.5% [one
eighth] on the average must be 1s, and no more than 15 consecutive zeros can
occur) can be met using the B9ZS algorithm. (B8ZS is a favorite of ISDN for
provision of the Clear 64 service.) With B8zs, deliberate bipolar violations in the
frame (192 bits of PCM plus one framing bit) are substituted whenever eight
consecutive zeros occur in the bit stream from which the frame signal is derived.
49
Inter-Tel 3000 T1 Training Self-Study Course
Bipolar Coding: In bipolar coding, alternating positive and negative pulses
represent one state (a binary 1). Absence of pulses in bipolar coding represents
the other state (binary 0).
Bipolar Violations (BPV): Any single-bit error can be detected, which is useful
since copper facilities are subject to a variety of natural (e.g. lightening) and
mechanical (induction motors, elevators, and power lines) noises. With bipolar
inversion, the polarity of any pulse must be opposite to the polarity of the
preceding pulse, and the pulse is nominally 3 volts in absolute amplitude. If an
error occurs in a 1-bit position, thereby converting it to a 0, adjacent 1s will be of
identical polarity, which is easily detectable, since it violates the polarity rule. If an
error occurs in a 0, converting it to a 1, there will also be two consecutive 1s of
identical polarity, which also violates the polarity rule. These are called “bipolar
violations,” or BVPs.
Bit Robbing: In North America, the least significant bit in every sixth sample per
voice channel is devoted to signaling.
Buffer: There is a bulk data memory in the T1 multiplexer. It provides data bit
storage that can be read and written between the channels and the aggregate
Time Division Multiplexed link.
Calling Party Number Service: This service provides the calling party’s line
number (not billing number) to the called party.
Channel Bank: Channel Banks are a bridge between the analog and digital
worlds, and have two basic functions. They convert analog voice to digital code,
and vice-versa. They also combine, or multiplex, the resulting digital streams
from several active sessions (voice or data) onto a single stream. They are a
combination of the digital terminals and the digital multiplex function.
Channel Bypass: Channel Bypass handles the routing of channels from
destination A to destinations B and C somewhat differently. Channels earmarked
for B are demultiplexed at the B-site multiplexer, while channels destined for C
bypass the demultiplexing function at site B and are routed directly to destination
C.
Channel Interface Unit: Channel Interface Units are ports that provide the
physical level connection of equipment, either voice or data, to the T1
multiplexer. Channel interface units are available for synchronous data and
asynchronous data using several types of interfaces or connectors.
Channel Pulse Stuffing: Channel Pulse Stuffing uses a data channel between
end points of a network that runs at a slightly higher rate than the input channel
speed. The data channel can carry all input data, plus some variable number of
bits or “stuff bits.” These bits are inserted to “pad” the input data stream to a
higher rate. This technique is used for T-3 and T-4 channels between central
offices.
Channel Service Unit (CSU): The Channel Service Unit (CSU) interfaces the
transmission facility (T1 span) to the user’s termination equipment (channel bank,
T1 multiplexer, a digital cross-connect system, or a PBX). In digital transmission,
precise synchronization is essential, and the CSU is a key element of this
synchronization process. Basically, the CSU ensures a high-quality digital signal
is sustained into and out of the network.
50
Inter-Tel 3000 T1 Training Self-Study Course
Cyclical Redundancy Check (CRC): The Cyclical Redundancy Check (CRC)
uses 2,000 bps and detects approximately 98.4% of all single and multiple errors.
The CRC-6 also provides false-frame protection.
D-Channel: The data channel, or D-channel, carries the signaling information at
64 kbps for the B-channels in a Primary Rate Interface, or at 16 kbps in a Basic
Rate Interface.
D-Channel Backup: Because the D-channel supports the other channels in the
ISDN network, loss of the D-channel would cause loss of access to the ISDN
circuits. D-Channels can be backed up to provide protection in the event of Dchannel loss. D-channel backup is especially important in Non-Facility
Associated Signaling (NFAS), because the D-channel supports all of the Bchannels in the entire network.
D4 Format: In the D4 Format, 24 channels are transmitted with 8 bits per
channel, plus one framing bit for synchronization every 125 microseconds (one
frame every 125 microseconds). This is repeated 8,000 times per second (1
second = 8,000 125-microsecond intervals) to produce 1,544,000 total bps (193
bits x 8,000 times per second = 1,544,000 bps).
D4 Superframe: A Superframe is a repeating sequence of 12 frames and thus
contains 12 framing/signal bits (the 193rd bit of each frame). One frame
corresponds to 125 microseconds. One superframe is thus 1.5 milliseconds in
duration. Each frame contains one synchronization bit to allow the receiving
equipment to decode, demultiplex, and allocate the incoming bits to the
appropriate channels.
Data Link: The Data Link (also called the Embedded Operations Channel) uses
4,000 bps for maintenance information, supervisory control and other future
needs.
Dedicated Access: With T1 access, the customer dials a long distance number
and the call goes directly to the long distance company. The user is charged a
flat monthly rate for access. Since the LEC is not switching the calls, that
percentage is dropped from the price of the call charged to the user. If the calling
volume warrants paying the monthly access charge, the user can save on long
distance calls.
Dedicated Service: Dedicated Service reserves a group of B-channels for a
specific function, such as outgoing calls.
Dialed Number Identification Service (DNIS): DNIS identifies the number the
caller dialed to reach your location. The system receives a base number and a
specified number of digits that identify the dialed number. *DNIS* is a form of
DNIS that does not have a requisite number of digits. The system receives a star
(*) before the DNIS digits to signal the beginning of the dialed number. A second
start after the digits serves to signal the end of the DNIS information.
Diverse Routing: With T1 access, the customer dials a long distance number
and the call goes directly to the long distance company. The user is charged a
flat monthly rate for access. Since the LEC is not switching the calls, that
percentage is dropped from the price of the call charged to the user. If the calling
volume warrants paying the monthly access charge, the user can save on long
distance calls.
51
Inter-Tel 3000 T1 Training Self-Study Course
Drop and Insert: The multiplexer at point B must be able to selectively remove
and insert traffic from the appropriate channels (drop and insert) and pass the
remainder along to point C (bypass).
DS 1: The DS1 (1,544,000 bps) D4 format is used to transmit 24 separate
channels of PCM voice or digital data. Each channel is transmitted 8 bits at a
time. All 24 channels are grouped together to form a group of 192 bits (24
channels times 8 bits). For synchronization of both end span equipment, every
group of 192 bits is preceded by a framing bit (F-bit). Together, all 193 bits make
up a FRAME.
Extended Superframe Format (ESF): In addition to benefiting end users
indirectly by offering a more reliable digital service, ESF allows the use of the
bandwidth to provide more advanced services. Unlike the D4 Superframe which
requires 8 bps for housekeeping, ESF requires only 2,000 bps. This implies that
the other 6,000 bps become available for other service-related purposes. Among
these services might be users’ ability to reconfigure their networks in real time
from a data terminal.
Flexible Billing: Flexible billing allows a 900 subscriber to modify a call’s billing
rate while speaking with the caller.
Fractional T1 (FT1): Fractional T1 provides for the transportation of subsets (or
fractions) of a 1,544,000 bps T1 data stream. The service allows users to
purchase only the number of channels required without paying the cost of a full
T1 span. Fractional T1 allows the user to buy individual channels rather than T1
spans of 24 channels.
Frame Builder/Multiplexer: The frame builder, sometimes called the Time Slot
Interchanger (TSI), multiplexes the information from the channel interface units
into an aggregate for transmission over the T1 link. It also demultiplexes the
received aggregate into separate channels. The most common framing format is
D4 format. This module usually is referred to as a T1 Aggregate Card.
Frame Slips: Synchronization of the network at the T1 level is achieved by
framing (D4 or ESF in North America) the data streams and frequency locking
the node and network clocks. Loss of synchronization results in “frame slips.”
Framing Bits: The framing bits are called BFfs, and the signaling bits are BFs.
BFfs are the odd-numbered framing bits, and BFs are the even-numbered bits.
The 12-bit word is used for synchronization and for identifying frame numbers 6
and 12, which contain channel-signaling bits.
Frequency Locked: T1 networks are designed to be synchronous networks.
That is, data clocked in at one point in the network has a fixed timing relationship
to the pint in the network at which the data is clocked out. This means that the
speeds at both points are the same, and there is always a fixed frequency
relationship between clocks that transmit and receive the data. This is usually
referred to as “frequency locked.”
Full Duplex: T1 links always operate in full duplex mode, where data traffic flows
in both directions.
52
Inter-Tel 3000 T1 Training Self-Study Course
H0 and H11: These are switched digital service types that combine contiguous
B-channels into a single bit stream. H0 combines six channels into a 384 kbps bit
stream. H11 combines 24 channels into a 1536 kbps bit stream. Applications for
these services include video conferencing and LAN connections.
Integrated Services Digital Network (ISDN): ISDN is a network of channels
that can provide simultaneous voice, data and video communication.
Jitter: No matter how stable the clocks are at both ends of a digital transmission
system, certain amounts of instability occur in the received signal. Typical causes
are path length changes, receiver noise and repeater regenerator inaccuracies.
There is a simple way of viewing jitter on a T1 circuit. Jitter implies that the start
and end times of the bit are not always exactly where they should be at the same
time. The signal actually jitters back and forth with respect to the rise and fall time
of the signal. This degradation is also called phase jitter.
Load Sharing: The links are sometimes set up in a “load sharing” configuration
where the traffic is routed over both links more or less equally. This arrangement
also provides an automatic backup for when one link fails; all traffic is sent over
the remaining operational links.
Loop Back: Loop back is the return of information back to the source at any one
of a number of locations in the network.
Master Slave Clocking: In this typical configuration, the network master
reference frequency is transmitted to selected slave nodes. These nodes
synchronize their clocks to the reference and pass on to lower level nodes the
network timing by way of the T1 transmission links. The process of passing the
reference downward from one level to another is referenced as master-slave
synchronization.
Mesh Network: Mesh Networks are similar to ring networks, but have additional
T1 links to interconnect each T1 multiplexer directly with every other multiplexer.
The mesh topology is the ultimate in redundancy and offers the added benefit of
minimum transmit time for information to flow through the network. This is done
to ensure the connection is given the shortest available path as network loading
changes.
Multi-Rate ISDN: This type of switched digital service allows the user to dial up,
on demand, any number of combined B-channels.
NX 64 kbps: This switched digital service type combines the B-channels into a
single bit stream. Applications for this service include video conferencing and
LAN connections.
Network Keep Alive: The FCC Rules, Part 68, require the Channel Service Unit
(CSU) to provide certain network functions. In the event of termination equipment
failure, the CSU must send a continuous stream of one pulse, called “Network
Keep Alive,” to the T1 span and Central Office.
Non-Facility Associated Signaling (NFAS): When a site uses several Primary
Rate Interface circuits, the D-channel on one circuit can support the B-channels
on other circuits, providing one additional B-channel on a span. That is, 24 Bchannels instead of 23B+D. This is called Non-Facility Associated Signaling, or
NFAS. This arrangement also requires D-channel backup
53
Inter-Tel 3000 T1 Training Self-Study Course
Office Repeater: The office repeater regenerates the signal for routing and
switching within the central office. The office repeater ensures that the T1 data
stream complies with 1.544 Mbps pulse shape requirements, as defined in AT&T
Publication 62411.
On-Demand B-Channels Selection: This feature allows on-demand allocation
of B-channels. With on-demand B-channel selection, all B-channel trunks can be
assigned to one trunk group and then programmed to be used as needed (ARS
outgoing access, etc.). This can be combined with Dedicated Service.
Ones Density Requirement: In North America, this is referred to as the “ones
density requirement” to maintain synchronization. At least 12.5% (one eighth), on
average, must be binary ones and there can be no more than 15 consecutive
binary zeros.
PCM Sampling: Of the 8,000 samples per second, 6,667 samples are 8-bits of
information, 1,333 samples are 7 bits of information, and 1 signaling bit. (6,667
samples of 8 bits = 53,336 bits of information + 1,333 samples of 7 bits = 9,331
bits of information + 1,333 signaling bits = 64,000 bps.)
Plesiochronous Timing: A plesiochronous (please-e-ock-ronus) does not
synchronize the network but uses highly accurate clocks at each node so the slip
rate between nodes is an acceptable low. These clocks are very expensive and
would be needed at every node. This method wasn’t chosen for implementation
in North America.
Point-to-Multipoint Network: When the full 24-channel capacity of a T1 link is
not needed at some of the remote locations, a point-to-multipoint network can be
the most cost-effective configuration. These networks are similar to multidrop or
multipoint links used in analog modem networks. The T1 links are routed from
point A to point B, from B to C, and so on.
Point-to-Point Networking: The most basic form of T1 network is the point-topoint link. One T1 multiplexer is at point A, a single 1.544 Mbps communications
link, and another T1 multiplexer is at point B. The channels, or ports, can be
connected, in any combination of voice, data, facsimile, or video applications,
based on the capability of the termination equipment.
Primary Rate Interface (PRI): This is the ISDN circuit providing B-channels that
can carry voice, data and video simultaneously. It also has one D-channel for
out-of-band signaling and packet data. See also 23B+D and 30B+D.
Primary Rate Interface Nodal/Centrex Express: This service type allows
communication between a PBX System and a Centrex System.
Private Line Integration: This allows systems to have private lines using
individual channels. The D-channel is not used on the private lines.
Pulse Code Modulation: The CODEC samples the analog voice signal 8,000
times per second and produces an eight-bit digital representation of each sample
called Pulse Code Modulation (PCM). The result is a 64,000 bit per second
stream of digital pulses called a DS0 or a digital signal level zero.
54
Inter-Tel 3000 T1 Training Self-Study Course
Repeater: Repeaters for digital signals are called “regenerative repeaters” since
they create brand new pulses to send along the line. The repeaters examine
each incoming “smeared” pulse and decide whether the pulse is a binary one or
zero. Based on the decision made, either a brand new one or zero is created and
sent along the line. Noise or other impairments are not amplified and also sent
along as with analog transmissions. Repeaters are usually placed about one mile
apart to be able to reliably regenerate the 1,544,000 pulses per second.
Ring Network: Multiple aggregate T1 multiplexers can also be arranged to form
ring networks. The ring topology provides “built-in” link redundancy. When one
T1 link fails in the ring, the traffic can be rerouted around the ring in the reverse
direction and still get to the destination. Ring networks also utilize the drop and
insert and bypass features to remove and place traffic onto the network.
Star Network: When many point-to-point links terminate at a central location, the
network is called a star network. The multiplexers may be single aggregate or
multiple aggregate, but they are all operating on simple point-to-point links. The
star topology is one of the most expensive in terms of line costs when long
distances to the remote locations are involved. When many point-to-point links
terminate at a central location, the network is called a star network.
Switched Access: With switched access, when the customer picks up the
phone and dials a long distance number, the LEC takes the call and sends it to
the long distance carrier. They “switch” the call. The long distance company is
charged a percentage for switching the call and that charge is built into the cost
per minute to the user.
Switched Digital Services: Switched digital services provide ISDN over a single
telephone line by combining several B-channels into a single bit stream.
Switched digital service types include H0, H11 Multirate, and N X 64 kbps.
Synchronization: Synchronization keeps the multiplexers at each end of the link
channel-locked with each other, so that what goes in at one end, on a specific
channel, comes out the same at the other end.
T1 Line Interface: The primary function of the T1 line interface is to convert the
aggregate stream, from the frame builder/multiplexer, to a format suitable for T1
transmission. This includes converting the signals from unipolar to bipolar format,
controlling link transmit and receive functions, framing control, and ensuring
sufficient ones density.
T1 Link: The term T1 refers to a specific digital method of transmitting voice and
data over 24 channels at 1,544,000 bits per seconds.
Time Division Multiplexer: A Time Division Multiplexer (TDM) divides the Tcarrier into equal time slices, and assigns one time slot to each channel. The
TDM takes the information from each channel, in sequence, and places it into a
time slot on the T-carrier. Another TDM at the other end of the link receives the
aggregate stream and sorts it out into the original channels.
Two-Stage Caller Identification (*ANI*DNIS*): This is a two-stage address
service providing both the callers telephone number and the dialed number. It
combines the *ANI* and the *DNIS* features.
55
Inter-Tel 3000 T1 Training Self-Study Course
User-to-User Information (UUI): This type of ISDN service allows two users to
share and manipulate data information over the D-channel while maintaining a
voice connection on a B-channel. For example, both parties can view the same
document, discuss it, edit it and see the changes as they’re made.
Wide Area Automatic Call Distribution (ACD): This service can distribute calls
to provide faster service. Wide Area ACD allows the calls to be sent to other
PBXs in the network.
56
Inter-Tel 3000 T1 Training Self-Study Course
Practice Exam Questions
Now that you have reviewed the material, complete the following practice exam.
Answer each question, referring to the information provided in this tutorial to find
the best answer. (The answer key is at the end of the test.)
The final Inter-Tel 3000 T1 certification exam is available on your CD or online at:
www.inter-tel3000.com
Being certified on Inter-Tel 3000 T1 entitles you to call Inter-Tel’s Technical
Support department when you need assistance. Your certification will be verified
at the start of your call.
1. You are installing voice-only T1 service. What is required for you to have voice
connection on the Inter-Tel 3000?
A. An external CSU
B. A CSU that splits voice and data
C. Both types of CSU
D. No additional equipment
2. If you purchased a T1 service for voice and data from your ISP and they provided a
CSU that splits the connection into separate voice and data elements, what Inter-Tel
3000 equipment is required?
A. A CO Module and a T1/PRI Module
B. A CO Module and an Internet Module
C. A T1/PRI Module and an Internet Module
D. All three Modules
3. When ordering a T1 span, the user must specify the coding method to be used on
the span. What are the two available coding methods?
A. ABM and D7SZ
B. IMA and S8BZ
C. AMI and B8ZS
D. AZS and BMIS
4. A T1 can be transmitted over long distances by using _______________.
A. Modems
B. Regenerative Repeaters
C. Multiplexers
D. Routers
57
Inter-Tel 3000 T1 Training Self-Study Course
5. When ordering a T1 span, the user must specify the framing scheme to be used on
the span. There are two schemes available. They are the D4 Superframe and the
_________________.
A. B8ZS Superframe
B. Extended Superframe
C. AMI Superframe
D. B7 Superframe
6. Analog voice signal is converted to ones and zeros (digital) by a device known as a
___________________.
A. Multiplexer
B. CODEC
C. Channel Service Unit
D. Repeater
7. The process of passing the Master Node Clock reference downward from one level to
another is referenced as ______________ synchronization.
A. Network Master Clocking
B. Network-Wide pulse stuffing
C. Master - Slave
D. Plesiochronous
8. Fractional T1 allows users to ___________________.
A. Buy and use individual channels
B. Use two circuits on one channel
C. Use one half of a channel
D. None of the above
9. Valid T1 Network topologies are _____________________.
A. Mesh
B. Ring
C. Point-to-Point
D. All of the above
10. When would you recommend using fractional T1?
A. When a customer’s long distance charges are very high
B. When they have high-volume traffic
C. When they have low-to-medium traffic
D. Never, because fractional T1 is no longer available
58
Inter-Tel 3000 T1 Training Self-Study Course
11. Using D4 Superframe format, what values are the A&B signaling bits set at when a
circuit goes off hook? A= _______________. B = ________________.
A. 1, 1
B. 0, 0
C. 0, 1
D. 1, 0
12. The existing world-wide standard for digital voice is ______________.
A. Pulse Amplitude Modulation (PAM)
B. Pulse Code Modulation (PCM)
C. Digital Modulation (DDM)
D. Frequency Division Multiplexing (FDM)
13. The frequency spectrum of analog voice, which is sent over a T1 span, is
_____________ to ______________.
A. 50, 15000
B. 300, 3000
C. 3000, 15000
D. 50, 3000
14. Using Extended Superframe format, the Data Link Portion uses __________ bps for
maintenance information, supervisory control and future needs.
A. 8000
B. 4000
C. 6000
D. 2000
15. The connection between Terminal Equipment 1 (TE1) or a Terminal Adapter (TA)
and a Network Termination 2 (NT 2) is called the __________ Reference Point.
A. R
B. V
C. T
D. S
59
Inter-Tel 3000 T1 Training Self-Study Course
16. The PRI operates at the standard North American DS1 transmission rate of
______________ and uses the same transmission specification as a T1 Carrier
Span.
A. 64kbps
B. 1.544mbps
C. 56kbps
D. C. 128kbps
17. A ______________ ____________________ is required to connect an ISDN
network’s NT1/NT2 to a non-ISDN compatible device.
A. Terminal Equipment 2
B. Network Termination 1
C. Terminal Adapter
D. Terminal Equipment 1
18. The OSI Reference Model defines the _______________ layers of the protocol stack
required for communications between systems.
A. Three
B. Five
C. Seven
D. Nine
19. The connection point between a non-ISDN terminal (PC w/modem, fax, credit card
reader, etc.) and a terminal adapter (TA) is called the ___________ reference point.
A. S
B. T
C. R
D. V
20. Layer 4 of the OSI Reference Model, referred to as the ________________
__________, is responsible for connection between the end points of the system.
A. Session Layer
B. Connection Layer
C. Network Layer
D. Transport Layer
60
Inter-Tel 3000 T1 Training Self-Study Course
21. The D-channel, or “_________” channel, carries the out-of-band signaling and call
control information for the ISDN interface.
A. Delimiter
B. Data
C. Diagnostic
D. None of the above
22. The connection between the Network Termination 1 (NT 1) and the ISDN Terminal
(TE 1) is called the ________ Reference Point.
A. R
B. T
C. U
D. V
23. A T1 span that is used for delivering ISDN must be configured for ________,
_________.
A. ESF, B8ZS
B. D4, AMI
C. ESF, AMI
D. None of the above
24. Your customer’s T1 service is as follows:
• Framing is set as D4 Superframe.
• Coding is set as AMI.
• Line Build-Out is set at -7.5dB.
• The Line Type is Loop Start with Caller ID.
• The Line gain is set at -3dB.
• Dialing is set at DTMF
Do you need to program any of the system parameters, or can you use the default
settings?
A. The default settings are correct for this installation
B. The Framing must be programmed.
C. The Line Type must be programmed.
D. All of the parameters must be programmed.
25. Can Called Number Routing be programmed for T1 and PRI?
A. No, only T1
B. No, only PRI
C. No, neither
D. Yes, both
61
Inter-Tel 3000 T1 Training Self-Study Course
ANSWER KEY
Question
Correct
Answer
1
D
2
B
3
C
4
B
5
B
6
B
7
C
8
A
9
D
10
C
11
D
12
B
13
B
14
B
15
D
16
B
17
C
18
C
19
C
20
D
21
B
22
B
23
A
24
C
25
D
62
Inter-Tel 3000 T1 Training Self-Study Course
Sample T1 Order Forms
Qwest DMS-100 Primary Rate Service Voice & Data Complex
Translations Form Instructions
Customer Name:
Enter the customer name
Address:
For basic PRS, enter the address this PRS will terminate. If
network System Integration, enter the address of the Carrier POP
or EU Location.
Order #:
Enter the SOP order number
Due Date:
Enter the due date of the service order (see CRIT date section in
methods).
Switch CLLI:
Enter the 11 digit CLLI of the Qwest switch this PRS will connect
to
Type of Svc:
Check the appropriate type of trunking, Dedicated or Call-By-Call.
Dedicated can be In-Only, Out-Only, or 2-Way voice and data.
Call-By-Call will have Inward and Outward voice and data. CallBy-Call trunks will be translated as two-way with software sizing of
Virtual Facility Groups controlling the number of trunks that have
inward or outward access. (See the Call-By-Call entry
instructions.)
Translation Protocol: DMS100 only provides Custom protocol
Configuration:
Enter the type of configuration. Enter the appropriate
configuration type and USOC. Valid Configuration Types are:
23B+D: 23 B channels and one D channel
23B + BUD: 23 B channels and a back up D channel
24B: 24 B channels
IID:
This is the Interface ID required per facility. This ID must match
the switch at the other end of the PRS. Data is 0 through the
number of facilities. If the customer is ordering all PRS configured
as 23B+D, the Interface ID will always be 0. If the PRS is
configured as 23B+BUD, the Interface ID will be 1. All 24B
configurations associated with a 23B+D and 23B+BUD, will start
at 2 and increase with the number of 24B's.
(Example: A customer wants a 23B+D. The Interface ID would
be 0 for each of the three facilities.)
(Example: A customer wants a 23B+D, a 23B+BUD, and three
24B facilities. The Interface ID would be 0 for the 23B+D, 1 for the
23B+BUD, and 2, 3, and 4 for the three 24Bs respectively.)
(Example: A customer wants a 23B+D and four 24Bs. The
Interface ID would be 0 for the 23B+D and 2, 3, and 4 for the four
24B's respectively.)
Customer's CPE
Enter the customer's CPE make and model that the PRS is
connecting to
Continued on next page
63
Inter-Tel 3000 T1 Training Self-Study Course
Qwest DMS-100 Primary Rate Service Voice & Data Complex
Translations Form Instructions Cont'd
Make & Model
L1 Flag
If the customer’s equipment is a Nortel SL-1 PBX or any other
manufacturer’s equipment this field must be set to YES. If the
customer’s equipment is a Nortel product other than SL-1 this field
must be set to NO.
IF Class:
Determines whether the DMS functions as the USER or
NETWORK. For DMS100 to PBX applications, the DMS is set as
NETWORK and PBX is user. For DMS100 to DMS100 or 5ESS
applications, the setting must be coordinated. This field must be
coordinated with the far end, as one end must be NETWORK and
the other must be USER
USDO
Enter the number of digits to be out pulsed by Qwest Switch
LCC:
1FB
= No Blocking
AS9
= 900/976 Block
AI9
= 900/976 & IDDD
ASL
= Toll Restriction
TCT
= Trk Call Trnsf.
PIC/LPIC:
Enter the appropriate Carrier Code
Qty of DID #s:
Enter the number of DID numbers being added, changed or
removed
LSO/FSO:
Enter the LSO of the central office that serves the customer
location. If this PRS is Foreign Exchange or Foreign Central Office,
enter the FSO of the central office from which the dial tone is
originating
DID # assigned:
Enter the DID number range being assigned and Route Index
Main Directory #:
The Main Directory Number is the established number the customer
wants displayed as the calling line ID. NOTE: The customer can
change this number. If the PBX is set to deliver Calling Party
Number information, the PBX will override the Main Directory
Number. If the customer does not want any calling party information
passed, the PBX must be set appropriately and the Main Directory
Number should be entered on this form as NONE.
Billing # (STN):
Must be customer working telephone number on premises. Can be
DID #. Will be used for 911 & billing toll charges.
Trunk Connections: Select the appropriate trunk type and indicate quantity.
Call-By-Call:
TGP number - enter the trunk group number (assigned by
Translations) NOTE: In the DMS100, the D-channel and all the Bchannels whose signaling is carried on that D-channel are in the
same trunk group.
Continued on next page
64
Inter-Tel 3000 T1 Training Self-Study Course
Qwest DMS-100 Primary Rate Service Voice & Data Complex
Translations Form Instructions Cont'd
I-VFG - Enter the Incoming Virtual Facility Group number and size.
(Documented on the order behind the /SFG FID. (Acts like a TGP)
O-VFG - Enter the Outgoing Virtual Facility Group number and size.
(Acts like a TGP)
I-OFRT Index - The incoming OFRT Index points to the incoming VFG
that accesses the customers DID numbers. (Acts like a Route Index)
O-OFRT Index- The outgoing OFRT Index is used to access the local
network and the customer’s toll provider (Interexchange Carrier).
(Acts like a Route Index)
Dedicated:
Enter the applicable TGP, RTI (assigned by Complex Translations),
and trunk #. NOTE: In the DMS100, the D channel and all B
channels whose signaling is carried on that D channel are in the same
TGP. If In or 2-Way, must have RTI. If Out TGP, enter N/A for RTI. If
this TGP will overflow to another TGP, enter the other TGP and RTI.
NOTE: A Voice service will overflow to another DSS or Analog TGP,
however, a Data service can only overflow to another PRS TGP.
Block CLID
Does the customer want to block inbound Caller ID information?
Hunting:
Customer's served by a DMS100 switch can order the following
hunting arrangements. Keep in mind that however the PBX is set to
hunt – the Central Office should be set up just the opposite. This is
needed in order to minimize glare.
Hunt Type
Description
LIDL
Hunt members are assigned a selection sequence of Least Idle. Least
Idle re-selects the last trunk used.
MIDL
Hunt members are assigned a selection sequence of Most Idle. Most
Idle distributes calls uniformly to all trunks in the group.
ASEQ
Hunt members are assigned a selection sequence of Ascending.
ASEQ select the first available trunk in the selection sequence
(ascending or descending).
DSEQ
Hunt members are assigned a selection sequence of Descending.
DSEQ select the first available trunk in the selection sequence
(ascending or descending).
CWCTH
Hunt members are assigned a selection sequence of Clock-wise
Circular. Clock-wise Circular will select the first trunk available after
the one most recently released.
CCWCTH
Hunt members are assigned a selection sequence of Counter Clockwise circular. Counter-clock Wise Circular will select the first trunk
available after the one most recently released.
Yield on Glare:
Which end should "give" when the Qwest switch and the customer's
switch attempt to seize a trunk at the same time?
65
Inter-Tel 3000 T1 Training Self-Study Course
66
Inter-Tel 3000 T1 Training Self-Study Course
Qwest 5ESS Primary Rate Service Voice & Data Complex
Translations Form Instructions
Customer Name:
Enter the customer name
Address:
For basic PRS, enter the address this PRS will terminate. If
Network System Integration, enter the address of the Carrier POP
or EU Location.
Order #:
Enter the SOP order number
Due Date:
Enter the due date of the service order (See CRIT date section in
methods).
Switch CLLI:
Enter the 11 digit CLLI of the switch this PRS will connect to
Type of Service:
Check the appropriate type of trunking.
Translation Protocol: Check the appropriate protocol, Custom or NI-2.
USDO:
Enter the number of digits to be out-pulsed by the Qwest switch
LCC:
1FB = No Blocking
AS9 = 900/976 Block
AI9
= 900/976 & IDDD
ASL = Toll Restriction
TCT = Trk Call Trnsf.
PIC/LPIC:
Enter the appropriate Carrier Code
Qty of DID:
Enter the number of DID numbers being added, changed, or
removed. For Uniform Access Solution or Circuit Switched Data
use a POTs number for DID. Any elaboration can be done in
Remarks.
LSO/FSO:
Enter the LSO of the central office that serves the customer
location.
If this PRS is Foreign exchange or Foreign Central Office, enter
the FSO of the central office from which the dial tone is
originating.
DID # assigned:
Enter the DID number range being assigned and Route Index
Main Directory #:
The Main Directory Number is the established number the
customer wants displayed as the calling line ID. The customer
can change this number. NOTE: If the PBX is set to deliver
Calling Party Number information, the PBX will override the Main
Directory Number. If the customer does not want any calling party
information passed, the PBX must be set appropriately and the
Main Directory Number should be entered on this form as NONE.
Billing Number (STN) Must be customer working telephone
number on premises. Can be DID #. Will be used for 911 and
billing toll charges.
Continued on next page
67
Inter-Tel 3000 T1 Training Self-Study Course
Qwest 5ESS Primary Rate Service Voice & Data Complex
Translations Form Instructions Cont'd
Trunk Connections:
Select appropriate trunk type and indicate quantity.
Call-By-Call:
TGP (Trunk Group Number) for the B channels and D Channel
(Assigned by Complex Translations).
TPOTS (In)/OPOTS (Out) TGP number and trunk number.
SFG (Simulated Facilities Number) and size must be entered.
MC Route Index on TPOTS points to the SFG group number. The
MC Route Index on the
OPOTS points to the local network and the customer Toll provider
(Interexchange Carrier). Both
MC Route Indexes are assigned by Translations and are not
reflected on service order.
If this TGP will overflow to another TGP, enter the other TGP and
RTI. NOTE: A Voice service will overflow to another DSS or
Analog TGP, however, a Data service can only overflow to
another PRS TGP.
Dedicated:
Enter the applicable TGP, RTI (assigned by Complex
Translations), and trunk #. If In or 2-Way, must have RTI. If Out
TGP, enter N/A for RTI. Also, enter the D Channel TGP. If this
TGP will overflow to another TGP, enter the other TGP and RTI.
NOTE: A Voice service will overflow to another DSS, however, a
Data service can only overflow to another PRS TGP.
Block CLID
Does the customer want to block inbound Caller ID information?
Hunting:
Customer's served by a number 5ESS switch can order the
following hunting arrangements. ISP’s requiring In-Only trunking
will always be set up a FIFO (First In First Out). Keep in mind that
however the PBX is set to hunt – the Central Office should be set
up just the opposite. This is needed in order to minimize glare.
Hunt Type
Description
Forward
A trunk is selected starting with the first trunk in the group in
ascending order.
Reverse
A trunk is selected starting with the last trunk in the group in
descending order.
UCD
Uniform Call Distribution. The start hunt member is randomly
selected, and then
hunting follows Forward Circular Sequential
Hunting.
Continued on next page
68
Inter-Tel 3000 T1 Training Self-Study Course
Qwest 5ESS Primary Rate Service Voice & Data Complex
Translations Form Instructions Cont'd
GUCD
Forward circular Sequential hunt. The hunt member is the last
selected member +1. Hunting then continues through the trunk
members in a forward direction using circular hunting to the
highest member, then starting over at the lowest member. The
hunt continues in this manner until an idle member is found or all
members are found busy.
BGUCD
Backward Circular Sequential. The start hunt member is the last
selected member -1. Hunting then continues through the trunk
members in a backward direction using circular hunting to the
lowest member, then starting over at the highest member. The
hunt continues in this manner until an idle is found or all the
members are found busy.
Yield on Glare:
Indicate which end should “give” when Qwest’s switch and
customer’s switch attempt to seize a trunk at the same time.
Additional Charges
The features listed below require an availability check of the
central office. There are also additional charges for these
features which the customer must be billed for.
Calling Name Delivery: Will provide name of caller if available. Billing USOC is entered
on associated DS1 order.
Redirecting Nbr Delry: When this capability is enabled, the Qwest switch will send an
extra element to the customers' equipment if the call has been
redirected (via a call forwarding feature). It will provide the
original number called as well as the last number that redirected
the call. Be careful in setting up this feature as it will sometimes
cause an adverse effect on the customers' voice mail
equipment. Today this capability is restricted to the 5ESS
switches and PRI groups using National Protocol. It is not
available on Custom. Billing USOC is entered on associated
DS1 order.
2B Channel Trans
This feature works like call transfer on other products. There is
however, a Telcordia (Bell Core) Specification GR2865-CORE
which the customers’ PBX must adhere to.
69
Inter-Tel 3000 T1 Training Self-Study Course
70