Adtran TSU LT User Manual
TSU LT
User Manual
Part Number 1202060L2-1
Document Number 1202060L2-1
February 1999
901 Explorer Boulevard
P. O. Box 140000
Huntsville, AL 35814-4000
Phone: (205) 963-8000
© 1999 ADTRAN, Inc.
All rights reserved.
Printed in USA.
ADTRAN Year 2000 (Y2K) Readiness Disclosure
ADTRAN has established a Year 2000 program to ensure that our products will
correctly function in the new millennium. ADTRAN warrants that all products
meet Y2K specifications regardless of model or revision.
Information about ADTRAN’s Y2K compliance program is available at the following locations:
ADTRAN Web Site www.adtran.com
Product Matrix www.adtran.com/y2kfax.html
Faxback Document
Line
Y2K Project Line (256) 963-2200
E-mail year2000@adtran.com
(256) 963-8200
Y2K plans and product certifications are
listed in the matrix.
iii
FCC regulations require that the following information be provided to the customer in this manual.
1. This equipment complies with Part 68 of the FCC rules.
The required label is attached to the bottom of the chassis.
2. If your TSU LT causes harm to the telephone network, the
telephone company may discontinue your service temporarily. If possible, they will notify you in advance. If
advance notice is not practical, you will be notified as soon
as possible. You will be advised of your right to file a complaint with the FCC.
3. Your telephone company may make changes in its facilities, equipment, operations, or procedures that could affect
the proper operation of your equipment. If they do, you
will be given advance notice so as to give you an opportunity to maintain uninterrupted service.
4. If you experience trouble with the TSU LT equipment,
please contact ADTRAN at (205) 963-8000 for repair/ warranty information. The telephone company may ask you to
disconnect the equipment from the network until the problem has been corrected, or until you are sure the equipment
is not malfunctioning.
5. This unit contains no user-serviceable parts.
6. An FCC compliant telephone cord and modular plug is
provided with this equipment. This equipment is designed
to be connected to the telephone network or premises wiring using a compatible modular jack which is Part 68 compliant. See installation instructions for details.
7. The following information may be required when applying
to your local telephone company for leased line facilities.
Service Type REN/SOC FIC USOC
1.544 Mbps - SF 6.0F 04DU9-BN RJ48C
1.544 Mbps - SF and B8ZS 6.0F 04DU9-DN RJ48C
1.544 Mbps - ESF 6.0F 04DU9-1KN RJ48C
1.544 Mbps - ESF 6.0F 04DU9-1SN RJ48C
iv
FEDERAL COMMUNICATIONS COMMISSION
RADIO FREQUENCY INTERFERENCE STATEMENT:
This equipment has been tested and found to comply with the limits for a Class
A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed
to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses,
and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio frequencies. Operation of this equipment in a residential area is likely to cause
harmful interference, in which case the user will be required to correct the interference at his own expense.
Shielded cables must be used with this unit to ensure compliance with Class A
FCC limits.
Changes or modifications to this unit not expressly approved by
the party responsible for compliance could void the user’s authority to operate the equipment.
v
CANADIAN EQUIPMENT LIMITATIONS
The Industry Canada Certification label identifies certified equipment. This certification means that the equipment meets certain
telecommunications network protective, operational, and safety
requirements. The Department does not guarantee the equipment
will operate to the user's satisfaction.
Before installing this equipment, users should ensure that it is permissible to be
connected to the facilities of the local telecommunications company. The equipment must also be installed using an acceptable method of connection. In some
cases, the company's inside wiring associated with a single line individual service may be extended by means of a certified connector assembly (telephone
extension cord). The customer should be aware that compliance with the above
conditions may not prevent degradation of service in some situations.
Repairs to certified equipment should be made by an authorized Canadian
maintenance facility designated by the supplier. Any repairs or alterations
made by the user to this equipment, or equipment malfunctions, may give the
telecommunications company cause to request the user to disconnect the equipment.
Users should ensure for their own protection that the electrical ground connections of the power utility, telephone lines and internal metallic waterpipe system, if present, are connected together. This precaution may be particularly
important in rural areas.
Users should not attempt to make such connections themselves,
but should contact the appropriate electric inspection authority,
or an electrician, as appropriate.
The Load Number (LN) assigned to each terminal device denotes the percentage of the total load to be connected to a telephone loop which is used by the
device, to prevent overloading. The termination on a loop may consist of any
combination of devices subject only to the equipment that the total of the LNs of
all devices does not exceed 100.
The ringer equivalence number (REN) assigned to each terminal adapter is
used to determine the total number of devices that may be connected to each
circuit. The sum of the RENs from all devices in the circuit should not exceed a
total of 5.0.
vi
IMPORTANT SAFETY INSTRUCTIONS
When using your telephone equipment, please follow these
basic safety precautions to reduce the risk of fire, electrical
shock, or personal injury:
1 Do not use this product near water, such as near a bath
tub, wash bowl, kitchen sink, laundry tub, in a wet basement, or near a swimming pool.
2 Avoid using a telephone (other than a cordless-type) dur-
ing an electrical storm. There is a remote risk of shock
from lightning.
3 Do not use the telephone to report a gas leak in the vicin-
ity of the leak.
4 Use only the power cord, power supply, and/or batteries
indicated in the manual. Do not dispose of batteries in a
fire. They may explode. Check with local codes for special disposal instructions.
SAVE THESE INSTRUCTIONS
vii
Warranty and Customer Service
ADTRAN will replace or repair this product within five years from the date of
shipment if the product does not meet its published specifications or if it fails
while in service. For detailed warranty, repair, and return information, see the
ADTRAN Equipment Warranty and Repair and Return Policy Procedure.
Return Material Authorization (RMA) is required prior to returning equipment
to ADTRAN.
For Service, RMA requests, or more information, contact one of the numbers
found at the inside back page of this manual.
viii
Tab l e of Co ntents
Chapter 1. Introduction .......................................................................................... 1-1
T1/FT1 Overview ..................................................................................................... 1-1
T1 Service Offerings........................................................................................... 1-1
Fractional T1........................................................................................................ 1-2
TSU LT Overview............................................................................................... 1-2
Functional Description .............................................................................. 1-2
TSU LT Rear Panel ............................................................................................. 1-4
TSU LT Features ................................................................................................. 1-5
TSU LT Interfaces............................................................................................... 1-5
Network Interface (NI) .............................................................................. 1-6
Nx56/64 Serial Interface ........................................................................... 1-6
Control Port Input ...................................................................................... 1-6
Chain Port Output ..................................................................................... 1-7
Software Management....................................................................................... 1-7
Front Panel .................................................................................................. 1-7
T-Watch Pro Management Software Program ....................................... 1-7
TSU LT Testing ................................................................................................... 1-8
Self-test ........................................................................................................ 1-8
Loopback Tests ........................................................................................... 1-8
DTE Interface Loopbacks ........................................................................ 1-10
Pattern Generation ........................................................................................... 1-11
Bridge/Router Application ............................................................................ 1-11
Chapter 2. Installation ............................................................................................ 2-1
Inspecting for Damages ........................................................................................... 2-1
Items Shipped by ADTRAN............................................................................. 2-1
Items Provided by Customer............................................................................ 2-1
Power Connection.............................................................................................. 2-2
Power Up Testing and Initialization ............................................................... 2-2
Self-test ........................................................................................................ 2-2
Chapter 3. Operation............................................................................................... 3-1
Operation ................................................................................................................... 3-1
General Menu Operation .................................................................................. 3-1
612020 60 L2 - 1 TSU LT User Ma nu al ix
Table of Contents
Menu Structure ...................................................................................................3-2
Four Opening Menu Functions ................................................................ 3-3
STATUS ....................................................................................................... 3-3
CONFIG .......................................................................................................3-3
UTIL ............................................................................................................. 3-3
TEST ............................................................................................................. 3-4
Menu Features .................................................................................................... 3-5
Data Field .................................................................................................... 3-5
Display Field ............................................................................................... 3-5
Arrows ......................................................................................................... 3-5
Example Menu Operations ....................................................................... 3-5
Front Panel ..........................................................................................................3-8
Chapter 4. Status Menu .......................................................................................... 4-1
STATUS ...................................................................................................................... 4-1
NI PERF RPTS.....................................................................................................4-2
CURR ERR/ALM ............................................................................................... 4-3
Alarms and Errors ...................................................................................... 4-4
ERR/ALM Hist ...................................................................................................4-5
Chapter 5. Configuration Menu............................................................................ 5-1
CONFIG ..................................................................................................................... 5-1
Network (NI)....................................................................................................... 5-2
FORMAT .....................................................................................................5-2
CODE ........................................................................................................... 5-2
YEL ALRM .................................................................................................. 5-2
XMIT ALRM ............................................................................................... 5-3
CLOCK SOURCE ....................................................................................... 5-3
BIT STUFFING ............................................................................................ 5-5
SET LBO ....................................................................................................... 5-5
RX SENSITIVITY ........................................................................................ 5-5
Unit ....................................................................................................................... 5-6
CNTRL PORT ............................................................................................. 5-6
POSITION of TSU LT ................................................................................ 5-6
MODEM INIT ............................................................................................. 5-7
DATA RATE ............................................................................................... 5-7
ALARMS .....................................................................................................5-7
TRAPS .......................................................................................................... 5-7
OUTPUT ...................................................................................................... 5-7
TEL NUM .................................................................................................... 5-8
Port ....................................................................................................................... 5-8
RATE 56/64 ................................................................................................. 5-8
x TSU LT User Manual 61202060L2-1
Table of Contents
CHANNELS ................................................................................................ 5-8
DTE TX CLK ............................................................................................... 5-9
START CHAN ............................................................................................ 5-9
# OF CHAN ................................................................................................. 5-9
DATA ........................................................................................................... 5-9
CTS ............................................................................................................. 5-10
DCD ........................................................................................................... 5-10
DSR ............................................................................................................. 5-10
INBAND .................................................................................................... 5-10
Chapter 6. Utility Menu .........................................................................................6-1
UTIL ............................................................................................................................ 6-1
Time/Date ........................................................................................................... 6-2
Software Rev ...................................................................................................... 6-2
Reinit Unit ........................................................................................................... 6-3
Address................................................................................................................ 6-3
Set Passcode ........................................................................................................ 6-3
Fact Restore ......................................................................................................... 6-3
Chapter 7. Test Menu.............................................................................................. 7-1
TEST ...........................................................................................................................7-1
Network Tests..................................................................................................... 7-2
LOCAL LOOPBCK .................................................................................... 7-2
REMOTE LOOPBCK ................................................................................. 7-2
TEST PATTERN ......................................................................................... 7-3
CLR ERRORS .............................................................................................. 7-4
INSERT 511 ERRORS ................................................................................7-4
Run Self-test ........................................................................................................ 7-4
Port Tests ............................................................................................................. 7-6
Chapter 8. Example Operations ............................................................................ 8-1
Testing Examples ...................................................................................................... 8-1
Far End Looped Back Test ................................................................................ 8-1
Network Interface Test ...................................................................................... 8-1
Appendix A. TSU LT Menu Tree....................................................................... A-1
Appendix B. DTE Data Rate Chart ..................................................................... B-1
Appendix C. Pinouts............................................................................................. C-1
Wiring ....................................................................................................................... C-1
Network.............................................................................................................. C-1
612020 60L2-1 TSU LT User Manua l xi
Table of Contents
Control-In/Chain-In ......................................................................................... C-2
Chain-Out ........................................................................................................... C-3
Nx56K/64K DTE (V.35).................................................................................... C-4
Index ...................................................................................................................Index-1
xii TSU LT User Manual 61202060L2-1
List of Figures
Figure 1-1. TSU LT Unit - Front View .................................................................... 1-3
Figure 1-2. TSU LT Rear Panel ................................................................................ 1-4
Figure 1-3. TSU LT Interfaces.................................................................................. 1-5
Figure 1-4. Network Loopback Tests ..................................................................... 1-9
Figure 1-5. DTE Interface Loopback .................................................................... 1-10
Figure 1-6. Simple Bridge Application on a T1 or FT1 Circuit..........................1-11
Figure 3-1. TSU LT Main Menus............................................................................. 3-1
Figure 3-2. TSU LT Main Menu Screen.................................................................. 3-2
Figure 3-3. Cursor on Menu Item. .......................................................................... 3-6
Figure 3-4. Submenu Fields..................................................................................... 3-6
Figure 3-5. Front Panel Layout ............................................................................... 3-8
Figure 4-1. Status Menu.......................................................................................... 4-1
Figure 4-2. Severely Errored Seconds Screen........................................................ 4-2
Figure 4-3. Loss of Signal (Current Errors/Alarms) Screens ............................. 4-3
Figure 4-4. Clear History Screen............................................................................. 4-5
Figure 5-1. Configuration Menu............................................................................. 5-1
Figure 5-2. Network Submenu ............................................................................... 5-2
Figure 5-3. Network Timed Clock Source ............................................................. 5-4
Figure 5-4. DTE Clock Source ................................................................................. 5-4
Figure 5-5. Internal Clock Source ........................................................................... 5-5
Figure 5-6. Configuration Submenu ...................................................................... 5-6
Figure 5-7. Inband Remote Configuration...........................................................5-11
Figure 6-1. Utility Menu .......................................................................................... 6-1
Figure 6-2. Time/Date Screen ................................................................................. 6-2
Figure 6-3. Address Screen ...................................................................................... 6-3
Figure 7-1. Test Menu............................................................................................... 7-1
Figure 7-2. Local Loopback Screen......................................................................... 7-2
Figure 7-3. Clear Errors Screen ............................................................................... 7-4
61202060L2-1 TSU LT User Manual xiii
List of Figures
Figure 7-4. Self Test Results Screen.........................................................................7-5
Figure 7-5. Loopback Setting Screen ...................................................................... 7-6
Figure 8-1. Main Menu with TEST Selected ......................................................... 8-2
Figure 8-2. Test Menu with NETWORK TESTS Selected.................................... 8-2
Figure 8-3. Local Loopback Test Menu .................................................................. 8-3
Figure 8-4. Remote Loopback Test Menu .............................................................. 8-3
Figure 8-5. Test Pattern Screen ................................................................................ 8-4
Figure 8-6. Clear Errors Screen ............................................................................... 8-5
Figure A-1. TSU LT Menu Tree (Status and Config)........................................... A-1
Figure A-2. TSU LT Menu Tree (Util and Test)....................................................A-2
xiv TSU LT User Manual 612 02060L2-1
List of Tables
Table 5-1. Normal Mode Operation.................................................................... 5-10
Table 6-1. Editing the Time/Date ..........................................................................6-2
Table B-1. DTE Data Rate vs. DS0s ........................................................................B-1
Table C-1. Network Pin Assignments .................................................................. C-1
Table C-2. Control-In/Chain-In Pin Assignments ............................................. C-2
Table C-3. Chain-Out Pin Assignments ............................................................... C-3
Table C-4. Primary V.35 Pin Assignment ............................................................ C-4
61202060L2-1 TSU LT User Manual xv
List of Tables
xvi TSU LT User Manual 61202060L2-1
Chapter 1
Introduction
T1/FT1 OVERVIEW
T1 digital communication links have been used by the
telephone companies (telcos) for voice transmission since the
early sixties. The D4 channel bank is an example of a T1
digital carrier system that was introduced in the midseventies and is still widely used by the telcos.
Communication demands of businesses continued to grow to
the point that the telcos began offering T1 service directly to
the public. D4 channel banks began to be used for T1 in
corporate network topographies for voice. The technological
advances in computer development also created a demand
for T1 data communication which now is a large part of the
T1 traffic.
T1 Service Offerings
T1 is a digital service that is delivered to the user over two
pairs of wires from the service provider. The signal operates
at 1.544 mega bits per second (Mbps) and is usually extended
by repeaters that are installed about every mile after the first
6000 feet. The T1 signal is divided into 24 time slots or digital
signal level zeros (DS0s) which operate at 64 kilo bits per
seconds (kbps). Each time slot is occupied by digitized voice
or by data.
1202060L2-1 TSU LT User Man ual 1-1
Fracti on al T1
Chapter 1. Introduc tion
The T1 signal originally used a type of framing known as D4
Superframe which identifies how the T1 is multiplexed.
Extended Superframe (ESF) is an enhancement of that
framing format. ESF provides a non-disruptive means of full
time monitoring on the digital facility. It was originally used
by the service provider to monitor the performance of their
service offering. Since the introduction of ESF, equipment
that is installed in private networks can also provide the
same performance information to the user.
Fractional T1 (FT1) allows the buyer to purchase less than a
full T1 circuit between two points. Most carriers offer
fractional T1 in increments of 56 or 64 kbps. Connection is
made to the same network elements. The network allows
multiple users to share the same interoffice T1 bandwidth.
FT1 remains almost exclusively an inter-exchange carrier
(IXC) service. Local exchange carriers (LECs) typically do
not offer FT1, so the user’s proximity to the IXC’s point-ofpresence (POP) is key in the savings that fractional T1 offers.
FT1 local access is available in two forms:
56 kbps
•
service (DDS) lines is extended from the IXC POP and
the bandwidth is combined at the office on an outbound
T1 circuit. The user pays for the individual 56K lines and
the amount of the interoffice T1 utilized
Full T1 line
•
the IXC POP and then only for the bandwidth utilized.
1-2 TSU LT User Manu al 1202060L2-1
- In 56 kbps the required number of digital data
- In T1 access, the user pays for a full T1 to
TSU LT Overview
This section provides a functional description of the TSU LT,
describes its features, and illustrates its four interfaces.
Functional Description
The ADTRAN TSU LT is one of several T1 multiplexers that
offer complete flexibility for connection of various data
sources to T1 or FT1 facilities. This family of TSU
multiplexers includes the following:
Chapter 1. Introduct ion
TSU LT
TSU
•
TSU LT -
and
T1 CSU/DSUs with a single Nx56K/
64K serial port.
TSU 100
•
- Same as the TSU with the added feature of a
slot in the rear panel to house an option module. Each
module offers up to four additional data ports.
TSU 600
•
- Same as the TSU with the added feature of six
slots in the rear panel to house up to six option modules.
Each module offers up to four additional data ports for a
total of 24 possible data ports.
CANCEL
ENTER
PWR
TD
TEST
ALM
ERR
CS
RS
RD
Figure 1-1. TSU L T Unit - Front View
The TSU LT serves as the link between user data sources such
as local area network (LAN) bridges and routers, computers,
CAD systems, and teleconferencing equipment. The amount
of bandwidth allocated to the port is custom programmable.
The data terminal equipment (DTE) data can occupy
contiguous or alternate channels in the T1 stream, and the
channels may start at any position.
1202060L2-1 TSU LT User Man ual 1-3
TSU LT Rear Panel
Number Identification for TSU LT Rear Panel
No. Item Function
1 Network T1-FT1 network interface
2 In Bantam test jack
3Out Bantam test jack
4 MON (Monitor) Bantam test jack
5 Chain-In Interface of chain-in
6 Chain-Out Connects to chain-in of another TSU LT
7 V.35 Nx56/64 DTE port
8 Power Switch Used to turn power on or off
9 Power Cord Captive 3-prong power cord
Chapter 1. Introduc tion
1 2 3 4 5 6 7 8 9
NETWORK
TEST JACKS CONTROL
IN OUT MON
CHAIN IN CHAIN OUT
V.35 Nx56/64
ONOFF
220VAC/60HZ
.075A
Figure 1-2. TSU LT Rear Panel
1-4 TSU LT User Manu al 1202060L2-1
TSU LT Features
• A DS1 interface and an Nx56/64 DTE serial interface port.
• Easy configuration capabilities using simplistic menus
displayed in a liquid crystal display (LCD) window operated by a front panel keypad.
• Timing is selectable from the network, from the Nx56/64
DTE port, or internally.
• All ones, all zeros, 511, and 1:8 test patterns.
• Extensive self-testing and monitoring ensures proper operation.
• Flexible channel allocation (any starting channel and alternate or contiguous).
TSU LT Interfaces
The TSU LT is equipped with four interfaces:
• Network DS1 interface per AT&T 62411
• Nx56/64 serial V.35 high speed interface
• Control input (EIA-232)/Chain port input
•Chain port output
See Figure 1-3 and the following descriptions in this section.
Chapter 1. Introduct ion
PC or Modem
Control
Chain
Input
Output
TSU
NI
Network
Nx56/64
Chain
Chain
Input
Output
TSU
NI
Nx56/64
Figure 1-3. TSU LT Interfaces
1202060L2-1 TSU LT User Man ual 1-5
Network Interface (NI)
The Network Interface (NI) port complies with the applicable
ANSI and AT&T standards:
• Alternate mark inversion (AMI) or binary 8 zero suppression (B8ZS) coding
• Automatic or manual line build-out
• Auto detect or manual settings for D4 or ESF framing
• Network performance monitoring and reporting
• Local and remote test loopbacks
• Extensive self-testing
Nx56/64 Serial Interface
Features of the Nx56/64 serial interface include:
• Data rates: N*56K or N*64K, where N=1 to 24 (DS0s)
• Inverted data (inverted high-level data link control
(HDLC)
•A V.35 interface
• Standard V.35 connectors
• Test loopbacks with 511 pattern generation and check
• Extensive self-testing
Chapter 1. Introduc tion
Control Port Input
Features of the control port input include:
• EIA-232 input from a personal computer (PC) or a modem for control of the TSU LT
• Chain input from another TSU LT
• Up to 9600 baud operation
• Input for PC proxy agent control or for a chained connection
1-6 TSU LT User Manu al 1202060L2-1
Chain Port Output
Features of the chain port output include:
• EIA-232 output to chain control to other TSU LTs
• Up to 9600 baud operation
• Automatic setup; no user input required
Software Manageme nt
Front Panel
The front panel provides complete and easy control of all
items that can be configured through menu-guided options.
The front panel LCD also displays the status of operation and
performance reports for the unit. A complete discussion of
the operation of the front panel is found in Chapter 3,
Operation on page 3-1. The menu options are found in
Chapters 4 through 7.
T-Watch Pro Management Softwar e Progr am
T-Watch Pro is the ADTRAN management software program
that allows the user to control the TSU LT from a PC. It
provides complete control over the configuration of the TSU
LT using a graphic interface. The T-Watch Pro program
displays the same status and performance data as the front
panel LCD. This data is displayed as tables and graphs.
Chapter 1. Introduct ion
The T-Watch Pro program has the following capabilities:
• Interfaces with a modem which permits dialing into a re-
mote TSU LT location to configure the unit or read the
unit’s status or performance.
• The performance data read from the units can be exported
in a file which is compatible with common spread sheet
programs.
1202060L2-1 TSU LT User Man ual 1-7
TSU LT Testing
The TSU LT offers three forms of testing:
• Self-test
• Loopback tests
• Pattern generation and check
Self-test
The self-test checks the integrity of the internal operation of
the electronic components by performing memory tests and
by sending and verifying data test patterns through all
internal interfaces. Although actual user data cannot be
passed during these tests, the self-test can run with the
network and DTE interfaces in place and without disturbing
any external interface.
The self-test automatically executes upon power up. It can
also be commanded from a front panel menu or from the
control port.
In addition to the specified self-tests, background tests are
also run on various parts of the internal electronics. These
run during normal operation to confirm continued correct
functioning. The background tests include:
Chapter 1. Introduc tion
• Monitoring the phase-locked loop for lock.
• Standard background network performance monitoring,
as required by ANSI T1.403 and AT&T 54016 for which
the results are stored.
Loopback Tests
A number of different loopbacks can be invoked locally from
the front panel, by T-Watch commands, or remotely by using
special inband codes. These include AT&T D4 network loop
up/loop down codes and V.54 loop up/loop down codes for
the Nx56K/64K serial interface. Additionally the loopbacks
can be remotely controlled by out-of-band commands via the
T1 ESF facility data link (FDL), or from T-Watch via a modem
1-8 TSU LT User Manu al 1202060L2-1
Chapter 1. Introduct ion
connection. Network and DTE interface loopbacks are
discussed in this section.
Network Loopbacks
There are three types of network loopbacks. See Figure 1-4.
Line Lo opbac k
Loops all of the received data back toward the network. The
transmitted data is the identical line code that was received,
including any bipolar violations or framing errors.
Payload Loopback
Similar to line loopback, except that the framing is extracted
from the received data and then regenerated for the transmitted data.
Data Loopback
Loops back all active DS0s and inserts idle code into unoccupied DS0s.
Figure 1-4. Network Loopback Tests
1202060L2-1 TSU LT User Man ual 1-9
DTE Interface Loopbacks
The Nx56K/64K serial interface offers a DTE loopback. See
Figure 1-5 on page 1- 10.
DTE Loopback
Loops all data from the DTE back towards the DTE. This
loopback may be initiated by the DTE asserting the local loopback (LL) input on the connector or by using the front panel
or T-Watch commands. The DTE (or the external test equipment) must provide a test pattern to check the DTE interface.
Chapter 1. Introduc tion
Figure 1-5. DTE Interface Loopback
1-10 TSU LT User Manu al 1202060L2-1
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