ATT System 25 Maintenance Manual

AT&T555-520-105
Issue 2, October 1987
AT&T SYSTEM 25
MAINTENANCE MANUAL 

©1987 AT&T
All Rights Reserved
Printed in USA
TO ORDER COPIES OF THIS DOCUMENT REFER TO DOCUMENT
NUMBER 555-520-105.
Contact: Your AT&T sales representative or
Call: 800-432-6600, Monday to Friday between 7:30 am
and 6:00 EST, or
Write: AT&T Customer Information Center
2855 North Franklin Road
P.O. Box 19901
Indianapolis, Indiana 46219
Every effort was made to ensure that the information in this document
was complete and accurate at the time of printing. However, information
is subject to change. This...

DANGER
Do not open the fan assembly or remove rear cabinet cover before
unplugging the cabinet from the electrical outlet. Wait at least five
minutes after unplugging the power cord before removing the rear
cover or power supply. The AT&T System 25 cabinets are not user
serviceable. Some voltages inside the cabinets are hazardous.
This equipment is to be serviced only by qualified technicians.
CUSTOMER WARNING
The Installation and Test Manual and the Maintenance Manual are
designed for use by qualified...

FCC NOTIFICATION AND REPAIR INFORMATION
AT&T SYSTEM 25
This telephone equipment is registered with the Federal Communications
Commission (FCC) in accordance with Part 68 of its Rules. In compliance
with the Rules, be advised of the following:
MEANS OF CONNECTION
Connection of this telephone equipment to the nationwide
telecommunications network shall be through a standard network interface
USOC RJ21X jack. Connection to private line network channels requires
USOC RJ2GX jack for tie lines or USOC RJ21X...

—
—The quantities and USOC numbers of the jacks required.
For each jack, provide the sequence in which lines are to be connected;
the type lines and the facility interface code and the ringer equivalence
number by position, when applicable.
This telephone equipment should not be used on coin telephone lines.
Connection to party line service is subject to state tariffs.
REPAIR INSTRUCTIONS
If you experience trouble with this telephone equipment, contact the AT&T
Business Customer Service Center on...

FCC REGISTRATION INFORMATION
Registration NumberAS593M-71565-MF-E
Ringer Equivalence
0.5A
Network InterfaceRJ21X or RJ2GX
PRIVATE LINE SERVICE
Service Order Code9.0F
Facility Interface Code
lTie LinesTL31M
lOff-Premises StationsOL13C
FCC WARNING STATEMENT
Federal Communications Commission (FCC) Rules require that you be
notified of the following:
l
l
lThis equipment generates, uses, and can radiate radio frequency energy
and, if not installed and used in accordance with the instruction manual,
may cause...

AT&T System 25 Maintenance
INTRODUCTION1-1
Organization1-2
Equipment Needed1-3
Assumption1-3
Precautions1-4
GENERAL MAINTENANCE INFORMATION
System Errors and Alarms
Error Log
Emergency Transfer
Alarm and Status Indicators
Switches and Test Points
System Administration Terminal
Maintenance Tests
2-1
2-2
2-2
2-3
2-3
2-4
2-4
2-5
SYSTEM HARDWARE
Overview
Digital Switch
Station Interconnect Panel
Trunk Access Equipment
Terminal Equipment
Wiring
Emergency Transfer Unit
3-1
3-1
3-3
3-3
3-5
3-7
3-7
3-7
-i- 

Digital Tape Unit3-8
Common Control and Switching Network3-8
Common Control3-10
Switching Network3-16
SYSTEM SOFTWARE
General
Switched Services Software
Administrative Software
Maintenance Software
Memory Allocation
Real-Time Constraints
Software Partitioning
Memory Circuit Pack
Call Processor Circuit Pack
TDM Bus
Port Circuit Packs
Step-By-Step Call Description
4-1
4-1
4-1
4-1
4-2
4-2
4-3
4-3
4-4
4-4
4-5
4-5
4-7
MAINTENANCE STRATEGY
General Procedures
Total System Failures
Port Problems
Common Control...

OPERATING THE DIGITAL TAPE UNIT7-1
Setting up the DTU7-1
Saving Translations7-2
Verifying Translations7-3
Restoring Translations7-4
CLEARING SYSTEM-DETECTED TROUBLES
General Trouble-Clearing Techniques
Consulting Error Log
Reseating and Replacing Circuit Packs
Removing and Restoring Power
Restarting the System
Interpreting Circuit Pack LEDs
Clearing Specific System Troubles
Complete System Failure
Common Control Trouble
Circuit Pack Trouble
Frontplane Ribbon Connector Trouble
Power Supply Trouble
Fan...

Trunk Troubles
Outgoing Trunk Problems
Incoming Trunk Problems
Error Log Interpretation: Loop Start Trunks
Error Log Interpretation: Ground Start
Trunks
DID Trunks Troubles
Special Port Circuit Options for Stations
and Trunks
Data Line Troubles
Multiple or Undiagnosable Troubles
9-5
9-5
9-6
9-6
9-7
9-8
9-9
9-11
9-13
REFERENCE DOCUMENTATION10-1
ABBREVIATIONS AND ACRONYMS11-1
GLOSSARY12-1
INDEX13-1
-iv-