AT&T System 25 R1V1_R1V2 Maintenance Manual

555-520-105 Issue 2, October 1987
AT&T SYSTEM
MAINTENANCE
25
MANUAL
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 PO. 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 document will be reissued periodically to incorporate changes.
Maintenance Manual Prepared by System 25 Document Development Group and the
AT&T Documentation Management Organization
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 service technicians only. Technician qualification includes completion of an AT&T hands-on instructor-led course covering installation and maintenance for this product. The use of these documents by anyone else might void the warranty.
Hazardous electrical voltages are present inside this product.
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
nationwide
Connection of this telephone equipment to telecommunications network shall be through a standard network interface USOC RJ21X jack. USOC RJ2GX jack for tie lines or USOC RJ21X jack for off-premises station lines. These can be ordered from your telephone company.
Connection to private line network channels requires
the
NOTIFICATION TO THE TELEPHONE COMPANY
If the system is to be connected to off-premises stations (OPSs), you must notify the telephone company of the OPS class of service, OL13C, and the service order code, 9.0F.
Upon the request of the telephone company, inform them of the following:
The Public Switched Network “lines” and the Private “lines” to which you will connect the telephone equipment.
—The telephone equipment’s “registration number” and “ringer
equivalence number” (REN) from the label on the equipment.
For private line connections, provide the facility interface code, TL31M for tie lines. You must also specify the service order code, 9.0F.
— 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 1-800-242-2121. The telephone
company may ask that you disconnect this equipment from the network until the problem has been corrected or until you are sure that this equipment is not malfunctioning.
RIGHTS OF
If your telephone telephone company may discontinue your service temporarily. If possible, they will notify you in advance. be notified as soon as possible. You will be informed of your right to file a complaint with the FCC.
Your telephone company may make changes in its facilities, equipment, operations, or procedures that could affect the proper functioning of your equipment. If they do, you will be notified in advance to give you an
opportunity to maintain uninterrupted telephone service. The voice terminals described in this manual are compatible with inductively coupled hearing aids as prescribed by the FCC.
THE TELEPHONE COMPANY
equipment causes harm to the telephone network, the
But if advance notice isn’t practical, you will
HEARING AID COMPATIBILITY
The voice terminals described in this manual are compatible with inductively coupled hearing aids as prescribed by the FCC.
FCC REGISTRATION INFORMATION
Registration Number AS593M-71565-MF-E Ringer Equivalence Network Interface
0.5A
RJ21X or RJ2GX
PRIVATE LINE SERVICE
Service Order Code
9.0F
Facility Interface Code
ŽTie Lines TL31M
•Off-Premises Stations
OL13C
FCC WARNING STATEMENT
Federal Communications Commission (FCC) Rules require that you be notified of the following:
This equipment generates, uses, and can radiate radio frequency energy
and, if not installed and used in accordance with the instruction manual, may cause interference to radio communications.
It has been tested and found to comply with the limits for a Class A
computing device pursuant to Subpart J of Part 15 of FCC Rules, which are designed to provide reasonable protection against such interference when operated in a commercial environment.
Operation of this equipment in a residential area is likely to cause
interference in which case the user at his or her own expense will be required to take whatever measures may be required to correct the
interference.
AT&T System 25 Maintenance
INTRODUCTION Organization Equipment Needed Assumption Precautions
GENERAL MAINTENANCE INFORMATION System Errors and Alarms Error Log Emergency Transfer
Alarm and Status Indicators Switches and Test Points System Administration Terminal Maintenance Tests
SYSTEM HARDWARE Overview Digital Switch
Station Interconnect Panel Trunk Access Equipment Terminal Equipment Wiring Emergency Transfer Unit
1-1 1-2 1-3 1-3 1-4
2-1 2-2 2-2 2-3 2-3
2-4 2-4 2-5
3-1 3-1 3-3 3-3
3-5 3-7 3-7 3-7
-i-
Digital Tape Unit Common Control and Switching Network
Common Control Switching Network
3-8 3-8 3-10 3-16
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
MAINTENANCE STRATEGY General Procedures Total System Failures Port Problems Common Control Problems Station, Wiring, and Trunk Problems Automatic Maintenance Tests Maintenance Failure
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
5-1
5-3 5-3 5-3 5-4 5-4 5-5 5-5
-ii-
ERROR LOG Accessing the Error Log From the SAT Error Log Dictionary
6-1 6-3 6-5
OPERATING THE DIGITAL TAPE UNIT
7-1
Setting up the DTU 7-1 Saving Translations Verifying Translations
Restoring Translations
7-2 7-3 7-4
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 Assembly Trouble Overheating Trouble Backplane and Cabinet Trouble Emergency Transfer Unit Trouble
CLEARING USER-REPORTED TROUBLES
Administration Equipment Troubles Time-Keeping Troubles Voice Terminal and Wiring Troubles Voice Transmission Troubles 7300H Series Terminal Troubles
8-1
8-1 8-1 8-1 8-3 8-4 8-8
8-9 8-9 8-9 8-11 8-12 8-12
8-17 8-18 8-18 8-26
9-1 9-1
9-2 9-2 9-3 9-4
-iii-
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 DOCUMENTATION
ABBREVIATIONS AND ACRONYMS
GLOSSARY
INDEX
10-1
11-1
12-1
13-1
-iv-
List of Figures
Figure 3-1. Figure 3-2.
Figure 3-3. Figure 3-4. Figure 3-5.
Figure 3-6.
Figure 3-7.
Figure 3-8. Figure 3-9.
Figure 3-10. Figure 3-11.
Figure 3-12.
Figure 3-13. Figure 3-14. Figure 3-15. Figure 3-16. Figure 3-17. Figure 3-18. Figure 3-19. Figure 3-20.
System 25 Block Diagram Typical Station Interconnect Panel (SIP)
Connections Trunk Access Equipment Connections System 25 Digital Switch Call Processor [ZTN82 (V1) or ZTN128
(V2)] Circuitry Memory [ZTN81 (V1) or ZTN127 (V2)]
Circuitry
TDM Bus Time Slot Generation (Not a
Timing Diagram) TDM Bus Diagram—3-Cabinet System Equipment Connected to System 25 By
Call Processor and Port Circuit
Packs Port Circuit Pack Common Circuitry Unique Ground Start Trunk (ZTN76)
Circuitry Unique Loop Start Trunk (ZTN77)
Circuitry Unique Tip Ring Line (ZTN78) Circuitry Unique ATL Line (ZTN79) Circuitry Unique Data Line (TN726) Circuitry Unique MET Line (TN735) Circuitry Unique Analog Line (TN742) Circuitry Unique DID Trunk (TN753) Circuitry Unique Tie Trunk (TN760B) Circuitry
Tie Trunk (TN760B) Circuit Pack Option
Switches
3-2
3-4 3-6 3-9
3-11
3-15
3-17 3-20
3-22 3-26
3-30
3-32 3-34 3-36 3-38
3-40 3-42 3-44 3-46
3-48
-v-
Figure 3-21.
Figure 3-22. Figure 3-23. Figure 3-24.
Unique Auxiliary Trunk (TN763)
Circuitry
Service Circuit (ZTN85)
Tone Detector (TN748) Circuit
Pooled Modem (TN758) Circuit
3-50 3-53 3-55 3-57
Figure 4-1.
Figure 5-1.
Figure 8-1. Figure 8-2. Figure 8-3.
Figure 8-4.
System Software Partitioning Response to System 25 Trouble Report AC Power Schematic
System Cabinet Backplane
TDM Signal Designations On Cabinet
Backplane
Power Designations On Cabinet
Backplane
4-6
5-2
8-15 8-19
8-21
8-22
-vi-
List of Tables
Table 3-A. Table 3-B.
Table 3-C.
Table 8-A.
Table 8-B. Table 8-C.
Table 9-A.
Table 9-B.
TDM Bus Time Slots TN760B Option Switch Settings and
Administration
Signaling Type Summary Displayed SAT Messages During Cold
or Warm Restart Circuit Pack Voltages—Symptoms 25-Pair Connector to Backplane
Designations Station/Trunk/Special Port Circuit
Board Options Applicable Actions for Circuit Board
Options
3-18
3-47 3-48
8-6
8-13
8-24
9-10
9-11
-vii-

INTRODUCTION

This manual provides the information necessary for monitoring, testing, and maintaining AT&T System 25 (Release 1 Version 1 and Release 1 Version 2). The modular self-testing capabilities of the system allow most maintenance to be reduced to simple procedures.
This issue replaces all previous issues of this manual. This manual is reissued to include changes in System 25 maintenance strategy that enhance product safety and to make minor corrections in the previous issue.
This manual replaces the AT&T System 25 Maintenance Manual (555-500-105). This manual includes information on Version 1 (V1) and Version 2 (V2). V2 is primarily a software upgrade that provides the following:
Enhanced Data Services
STARLAN NETWORK Access
Switched Loop Attendant Console
Virtual Facilities
Miscellaneous Changes/Enhancements.
Required hardware for V2 includes a ZTN128 Processor circuit pack and a ZTN127 Memory circuit pack. A ZTN84 STARLAN Interface circuit pack and a switched loop attendant console are optional.
The maintenance procedures include:
Observation of alarm conditions;
Analysis of error messages and test results;
Performance of restoration procedures;
Replacement of system components; and
Performance of tests.
This manual is intended for use by a maintenance technician dispatched to a System 25 site in response to an alarm or a user trouble report. The technician must have completed the Tier 1 training course (T-335).
1-1
INTRODUCTION
Each installed System 25 has a customer-designated System Administrator. The Administration and Implementation Manuals for your system describe the administrator’s functions.
The maintenance technician should work closely
with the System Administrator.

Organization

This manual is divided into 13 sections. follows:
Section 2. General Maintenance Information— Provides an overview of
alarms, maintenance concepts, equipment, and basic procedures.
The remaining sections are as
Section 3. System Hardware—
Describes the principal components of
the system, and provides detailed information on the switching network
and all circuit packs (CPs) supported by the system.
Section 4. System Software—
Describes the system software resources
including switched services software, administration software, and
maintenance software.
Section 5. Maintenance Strategy— Provides an overview of the
maintenance process.
Section 6. Error Log— Presents the format for error records and
examples of error messages with explanations.
Section 7. Operating the Digital Tape Unit— Provides operating
instructions for the digital tape recorder to save and restore translations.
Section 8. Clearing System-Detected Troubles— Provides general
trouble-clearing techniques and procedures for clearing specific system troubles.
Section 9. Clearing User-Reported Troubles— Describes user
complaints and provides procedures for clearing them.
Section 10. Reference Documentation— Provides a list of other
System 25 documentation that may be valuable to the maintenance
technician.
Section 11.
Abbreviations and Acronyms— Provides a list of
abbreviations and acronyms used in System 25 documentation.
Section 12. Glossary
Provides a definition of terms and acronyms
used in System 25 documentation.
1-2
INTRODUCTION
Section 13. Index— Provides an alphabetical listing of principal subjects
covered in this manual.

Equipment Needed

The following tools and equipment should be taken by the maintenance technician on any System 25 service call:
EIA breakout box
Digital voltmeter (KS-20599 or equivalent)
Modular cord breakout box
110-type punchdown tool (AT 8762D or equivalent)
Dracon TS21 or equivalent touch-tone test set
Assorted flat-head screwdrivers
Assorted Phillips-head screwdrivers
Long-nosed pliers
Regular pliers
Wrist grounding strap
Model DC4 Digital Tape Unit, with 355A adapter and a D8W cord (Comcode 404079429)
Administration terminal (TI 703KSR or equivalent), with 355A adapter (Comcode 404079436).
An oscilloscope is not needed for the Tier 1 maintenance procedures provided in this manual.

Assumption

The information provided in this manual assumes that the system was initially installed and tested in accordance with the Installation and Test Manual (555­520-100).
1-3
INTRODUCTION

Precautions

Electromagnetic fields radiating from the system cabinets may generate noise
in other communications equipment. The technician must be sure that all cabinet panels and covers maintenance.
WARNING: Electrostatic discharge can destroy or severely damage
integrated circuits or CPs.
The maintenance technician MUST ALWAYS WEAR A WRIST GROUNDING STRAP when handling CPs.
block at the back of the cabinet. electrostatic discharge may not be immediately apparent.
DANGER: Do not clip the wrist grounding strap to any cabinet location
other than the grounding block. Do not clip the wrist grounding cord to a CP.
are securely in place after performing
The cord must be attached to the grounding
Damage to integrated circuits via
1-4

GENERAL MAINTENANCE INFORMATION

The primary maintenance objective is to detect, report, and clear troubles as quickly as possible with minimum disruption to normal service. Periodic
system self-tests, detection hardware are several of the maintenance tools used to achieve this objective. The system design allows most troubles to be isolated to a replaceable unit.
The System 25 hardware is maintained as a group of independent units (that
is, maintenance objects). Each object is normally a separately replaceable unit. Examples include circuit packs (CPs), power supplies, fan assemblies,
the Digital Tape Unit, AC Power Distribution Unit, voice terminals, lines, and trunks.
There are two general categories of troubles in system maintenance:
System-Detected Errors
User-Reported Troubles.
For system-detected errors, a light-emitting diode (LED) on the Attendant Console is automatically lighted if the error qualifies as an “alarm.” This is a serious error. Most alarms are also indicated by LEDs on system CPs.
User-reported troubles usually result from service problems at individual voice and data terminals and are often related to alarmed conditions.
Error records and alarms are retired either automatically or manually. After a trouble or error has been cleared, the system retests the previously faulty area within a variable time interval. When the error is no longer detected, the error message, and alarm if applicable, is retired. Maintenance personnel may choose to retire error records and alarms manually after a problem has been fixed by entering commands at the System Administration Terminal (SAT). Using the SAT, error records can be accessed, listed, and removed. Certain errors may not be removed. On the other hand, some alarms must be cleared manually. After the error messages have been removed from the error tables, the Attendant Alarm LED (and red CP LEDs) will go dark—
unless the trouble recurs.
automatic software diagnostic programs, and fault
2-1
GENERAL MAINTENANCE INFORMATION

System Errors and Alarms

When a system maintenance object begins to fail periodic testing, the system automatically generates an error record. stored in one of three tables in the error log.
The three tables are:
Permanent System Alarms: These are failures that cause degradation of
service and require immediate attention. These alarms will light the Alarm LED on the Attendant Console and are stored in the Error Log Permanent System Alarm table. This type of alarm also lights a red LED on an associated CP. The LED, when lighted, is a visual signal that service is required.
Depending on severity, the record is
Transient System Errors:
These are potential failures that may cause degradation of service, although they do not light the Alarm LED on the Attendant Console. Transient System Errors are errors that have not yet been verified by system self-tests, and/or have not reached the level of a Permanent System Alarm.
If a Transient System Error is verified or reaches a certain threshold level of severity, it is reclassified as a Permanent System Alarm, and the Alarm LED on the Attendant Console lights. Transient system errors are stored in the Transient System Error table. The system stores up to 40 Permanent System Alarms and Transient System Errors in their respective tables in the error log.
Most Recent System Errors: These are the ten most recent errors
recorded by the system, regardless of their severity. They do not light
the Alarm LED on the Attendant Console, unless they escalate to a Permanent System Alarm.

Error Log

The three error tables can be displayed on the System Administration Terminal (SAT). The error tables are very useful in diagnosing and analyzing problems, particularly when the problem has not caused an alarm or when alarms cannot be retired by replacement of maintenance objects.
The error tables are organized by time of occurrence. Unresolved errors are listed, as well as past alarms providing a profile of past and current state of
the system. Example error records are provided in the Error Log description.
2-2
GENERAL MAINTENANCE INFORMATION

Emergency Transfer

System 25 has emergency transfer capability in case of total system outage. Emergency transfer connects preassigned single-line voice terminals directly
to trunks that are connected directly to the CO, bypassing the System 25.
Emergency transfer is invoked by loss of ac power or by any failure of the system that prevents it from processing calls.

Alarm and Status Indicators

Maintenance-related LED indicators are provided on the following equipment:
Attendant Console: A green Alarm LED is provided to indicate the
presence of a Permanent System Alarm. The LED flashes with each new alarm. The attendant can press the associated button to cause the LED to light steadily.
Circuit Packs (CPs): LEDs are provided on the front edge of the CPs.
The LEDs are visible when the front cover of the cabinet is removed. When lighted, these LEDs indicate the status of the CP as follows:
Port CPs:
— Red—”
On” several seconds during power up and test, “Off” with test pass, and “On” if fault in CP or associated trunk is detected.
— Green—”On” indicates call resource available (port capable
of processing calls).
— Yellow—”
On” indicates a call in progress, “Off” when not in
use.
— No LEDs Lighted—CP is not translated.
Memory CP—Red status LED—’’On” several seconds during
power up and test,
“Off” with test pass. After test pass, “On” if
fault in CP is detected.
Service Circuit CP—Same as port CPs except yellow LED flashes
(that is, flashes when busy). Steady “Off” indicates a CP problem. Steady “On” indicates a tone receiver is being used.
2-3
GENERAL MAINTENANCE INFORMATION
Call Processor CP—This CP has only a green LED that flashes,
except during test.
“Off” or “On” steady indicates a problem.
Refer to “Clearing System-Detected Troubles—Interpreting Circuit Pack LEDs” in Section 8 for additional information.
Power Supply: The cabinet power supply has a green LED that, when
lighted, indicates normal power operation.

Switches and Test Points

The power switch on the back of the cabinet controls cabinet ac power and should be left in the “On” position (1=“On”), except when otherwise indicated. The system has no other field accessible switches, fuses, or circuit breakers. The power supply contains its own fuses, but these are not field replaceable.
Newer models have voltage test points located on the upper right corner at
the front of the cabinet. Older models have test points on the backplane behind the rear cover.
These test points are factory use only! Under no circumstances should the
rear cover be removed to provide access to the test points unless the power
cord has first been unplugged.

System Administration Terminal

The SAT used to administer the system may also be used to read and clear the error log tables. The error log is read by logging on the SAT, selecting the main menu item “SEARCH,” and then selecting the table to be read (that
is, Permanent System Alarms, Transient System Errors, or Most Recent System Errors). To log on the SAT and access an error table, refer to the procedures provided in Section 6 “Error Log.”
2-4
GENERAL MAINTENANCE INFORMATION

Maintenance Tests

There are two classes of automatic maintenance tests: periodic and demand.
Periodic tests are run automatically at fixed intervals on a specific schedule
and do not affect service.
Demand tests are run by the system when it detects a need for them. Demand tests include the tests that are required only when trouble occurs. Some of the demand tests may be disruptive to system operation.
Maintenance personnel cannot initiate any of these automatic tests.
2-5

SYSTEM HARDWARE

Overview

Figure 3-1 is a block diagram of the major components of System 25. The major hardware components of the system are:
Digital Switch
Station Interconnect Panel (SIP)
Trunk Access Equipment (TAE)-includes 700A [110-type or 66-type
(157BF)] Connector Blocks and Network Access Facilities
Terminal Equipment
Wiring
Emergency Transfer Unit (ETU) *
Digital Tape Unit *
Common Control and Switching Network
System Administration Terminal (SAT) *
SMDR/Call Accounting System Output Device. *
* Optional Equipment Refer to the Reference Manual (555-520-200) for a complete description of the
system hardware.
Refer to the Installation and Test Manual (555-520-100) for
system grounding details.
3-1
SYSTEM HARDWARE
DIGITAL SWITCH
STARLAN CP (V2)
AUX TRUNK CP
DATA LINE CP
P/O SIP
SAT DTU
SMDR/CAS
STATION CP
CALL
PROCESSOR
CO
TRUNK CP
STATION CP
CO
TRUNK CP
STATION CP
(OPS)
TIE
TRUNK CP
LEGEND :
CAS -
CO ­DTU ­ETU ­OPS -
CALL ACCOUNTING SYSTEM CENTRAL OFFICE DIGITAL TAPE UNIT EMERGENCY TRANSFER UNIT OFF-PREMISES STATION
-48V
SIP
P/O SIP
66-TYPE
BLOCK
10B ETU
-48V CPU
TRK
LINE
P/O - PART OF SAT SIP
SMDR
NETWORK EXPANSION UNIT
AUXILIARY EQUIPMENT
RS-232C TERMINALS
VOICE TERMINALS, ADJUNCTS, AUXILIARY EQUIPMENT
SIP
700A (110-TYPE) OR
157BF (66-TYPE) BLOCKS
CO
- SYSTEM ADMINISTRATION TERMINAL
- STATION INTERCONNECT PANEL
- STATION MESSAGE DETAIL RECORDING
P/O SIP
NETWORK ACCESS
POWER FAILURE TERMINALS
RJ21X RJ21X
RJ21X
RJ2GX
CO
3-2
Figure 3-1.
System 25 Block Diagram
SYSTEM HARDWARE

Digital Switch

System 25 consists of up to 3 separate cabinets, each equipped with 12 universal slots for circuit packs (CPs). Each cabinet has its own power supply and fan assembly for cooling.
No auxiliary equipment or customer-
provided equipment is located in the cabinets.
The Common Control circuitry (Call Processor, Memory, and Service Circuit)
is located in Cabinet 1. Other CPs can be located in any slot in any cabinet, but certain rules are suggested (see Reference Manual). All CPs are replaceable from the front of the cabinet upon removal of the front cover.
An address plug inserted into the header on the cabinet’s backplane (lower center portion) designates the cabinet number. When plugged into slot #5, the cabinet is translated as Cabinet #1, slot #6 = Cabinet 2, and slot #7 = Cabinet #3.

Station Interconnect Panel

The Station Interconnect Panel (SIP) (Figure 3-2) provides connectivity between the digital switch and station equipment via the building wiring. Peripheral equipment is also generally connected to the system through the SIP.
The SIP consists of a group of 617A panels and associated adapters. The adapters support building wiring circuits that are either cutdown or modular. Octopus cables connect the system cabinets to the SIP. Adapters that can be mounted on the SIP are as follows:
Z210A—Six 4-pair modular jacks to six 4-pair modular jacks
858A—Six 4-pair modular jacks to six 110-type cutdown blocks.
3-3
SYSTEM HARDWARE
DIGITAL SWITCH
STATION CIRCUIT
PACK
C2
--
__
--
(1)
(8)
MODULAR
VOICE TERMINALS, ADJUNCTS, POWER UNITS
Figure 3-2.
3-4
JACKS
LEGEND:
C2 – OCTOPUS CABLE (WP90780) - PEC 2720-05P 858A ADAPTER (FURNISHED BY INSTALLER) -
SIX 4-PAIR MODULAR JACKS TO SIX 11O-TYPE CUTDOWN BLOCKS
Typical Station Interconnect Panel (SIP) Connections
SYSTEM HARDWARE

Trunk Access Equipment

The Trunk Access Equipment (TAE) (Figure 3-3) connects common carrier facilities to trunk CPS. The TAE consists of 700A Network Interface Blocks and Network Interface cables.
Connector Blocks are connected to RJ21X or RJ2GX network interfaces by 25-pair single-ended cables. 700A blocks into sets of up to eight trunks of the same type. These blocks are then connected to the cabinets with splitter cables.
The 700A [110-type or 66-type (157BF)]
Incoming central office trunks are sorted on the
3-5
SYSTEM HARDWARE
DIGITAL SWITCH
CO TRUNK FACILITIES PORT CP(S)
CO TRUNK FACILITIES PORT CP(S)
ANALOG
LINE CP
(TN742)
B
700A NETWORK
INTERFACE BLOCKS
(110-TYPE OR
66-TYPE)
I
I
I
__________ I I
I
I I
I
I A I
CO NETWORK INTERFACE
FACILITIES
(LOOP AND GRD. START TRUNKS,
OPS, DID TRUNKS)
I
I
I
RJ21X
———————
CENTRAL
OFFICE
TIE TRUNK FACILITIES PORT CP(S)
LEGEND:
Figure 3-3.
3-6
I I I
I
C
I
I I
SINGLE-ENDED 25-PAIR CONNECTOR CABLE (A25D)*
A-
3 TO 1 SPLITTER CONNECTORIZED CABLE (OR6016) - PEC 2720-06X
B-
2 TO 1 SPLITTER CONNECTORIZED CABLE (OR6015) - PEC 2720-05X
C-
OFF-PREMISES STATION
OPS -
STATION INTERCONNECT PANEL*
SIP -
D-
OCTOPUS CABLE (WP90780) - PEC 2720-05P INSIDE WIRE*
E­*-
FURNISHED BY INSTALLER
I
I A I
I
I I
RJ2GX
TIE LINE
I
—————
Trunk Access Equipment Connections

Terminal Equipment

SYSTEM HARDWARE
System Asynchronous Data Units (ADUs), data terminals, attendant consoles, and auxiliary equipment.
7300H series, Single-Line [Tip & Ring (touch-tone or rotary*)], and MET (Multibutton Electronic Telephone). connected to a compatible port CP.
ADUs provide the interface between the system and data equipment connected to the Data Line Circuit (TN726) ports. Single-line and 7300 series multiline voice terminals can also be connected to ADUs along with data equipment. Separate wire pairs in the ADU provide voice terminal connectivity back to the digital switch via the SIP. At the SIP, an adapter is used to separate the voice and data leads for connection to their respective system ports.
25 terminal
equipment
System 25 supports three types of voice terminals:
includes
Each type of voice terminal must be
various
voice terminals,

Wiring

The wiring plan is consistent with the Small Business Distribution System. The system uses 4-pair cables (24 AWG or 26 AWG) and cords as well as modular connectors and adapters. Various building wiring arrangements are supported, including new wiring, reuse, and modular.

Emergency Transfer Unit

The Emergency Transfer Unit (ETU) supports five power failure transfer
stations and a Direct Inward Dialing (DID) make busy function. A System 25 installation can have up to four ETUs. The ETU is activated if ac power fails
or if the system stops functioning.
*
If rotary-type voice terminals are used, System 25 features or services accessed by the # or *
button are not available to the user.
3-7
SYSTEM HARDWARE

Digital Tape Unit

The Model DC4 Digital Tape Unit (DTU) is required on all maintenance calls. It is used to save translations if the system fails. Translations should be saved on both the original and the backup tape cassette on a maintenance call (see Section 7 “Operating the Digital Tape Unit”).

Common Control and Switching Network

Figure 3-4 shows the System 25 digital switch.
The basic switch hardware consists of the following:
Common Control
— Memory Bus — Call Processor CP — Memory CP
Switching Network
— TDM (Time Division Multiplex) Bus — Port Circuits
3-8
— System Resources
MEMORY BUS
SYSTEM HARDWARE
COMMON
CONTROL
SWITCHING
NETWORK
Figure 3-4.
CALL PROCESSOR
PORT CIRCUITS
TRUNKS, VOICE TERMINALS, DATA TERMINALS
MEMORY
TDM BUS
System 25 Digital Switch
SERVICE CIRCUIT
TONE DETECTOR
SYSTEM RESOURCES
POOLED MODEM
3-9
SYSTEM HARDWARE

Common Control

The Common Control circuitry consists of the Call Processor [ZTN82 (V1) or ZTN128 (V2)] and Memory [ZTN81 (V1) or ZTN127 (V2)] circuit packs and associated memory bus.
Memory Bus
The memory bus is a 60-wire (including grounds), 39-bit (16-data, 23­address), 6-MHz frontplane flat ribbon cable.
Call Processor Circuit Pack [ZTN82 (V1) or ZTN128 (V2)]
The Call Processor runs the system feature software. It is powered from the backplane by +5 and -5 volts. It also draws drive the Emergency Transfer Unit. Processor CP. The Call Processor circuitry, as shown in Figure 3-5, includes:
Microprocessor
Memory management
On-board memory
EIA channels
Network controller
-48 volts from the backplane to
Each system must include one Call
Clock
Frontplane interface
Reset circuitry
Bus error circuitry
Interrupt circuitry
Emergency Transfer Unit Control.
3-10
INTERRUPT CIRCUITRY
SERIAL
CHANNEL
1
EIA CHANNELS
( RS-232C )
SERIAL SERIAL
CHANNEL CHANNEL
3
2
SYSTEM HARDWARE
TO EMERGENCY
TRANSFER UNIT
(ETU)
SERIAL
CHANNEL
4
-48V DC
ETU
CONTROL
BUS
ERROR
CIRCUITRY
RESET
CIRCUITRY
TDM BUS
LEADS
Figure 3-5.
MICROPROCESSOR
(68010)
PROCESSOR
NETWORK
CONTROLLER
SAKI
BUFFERS
BUS
READ ONLY
MEMORY
( 64K )
EIA
CONTROL
TIME OF
DAY
CLOCK
EIA
CONTROL
MEMORY
MANAGEMENT
RANDOM ACCESS MEMORY
(80K)
FRONT PLANE
INTERFACE
(BUS
BUFFERS)
+5V DC
BATTERY
(POWER
Call Processor [ZTN82 (V1) or ZTN128 (V2)] Circuitry
FAIL
DETECT)
TO MEMORY CIRCUIT PACK VIA FRONT PLANE BUS
3-11
SYSTEM HARDWARE
Microprocessor:
processing and data processing features.
administration, testing, and reporting software.
Memory Management:
Random Access Memory (RAM) into 1024 memory pages of 256 bytes each. Each page is read and write protected, generates bus errors when violated, and each is recappable allowing data areas to remain contiguous.
On-Board Memory:
Memory (ROM) containing the power-up tests and the switch operating system. In addition, there are 80 K bytes of protected RAM containing writable data storage for call processing. The RAM is backed up by an on­board trickle-charge battery that maintains memory contents for up to 2 months. Of the 80 K RAM, 24 K is dedicated to translation data. The remainder is dedicated to call status data and the operating system message queues.
EIA Channels: Four asynchronous RS-232C EIA ports (1-4) are included to
permit communication
terminal, a Station Message Detail Recording (SMDR) device, and a Digital Tape Unit.
Network Controller:
messages between the Call Processor and the port circuits over the TDM bus. The controller also monitors system clocks.
The controller includes an 8-bit microprocessor that acts as a throttle, passing messages between the Call Processor and the port board microprocessors.
A 68010 16-bit microprocessor that executes call
This includes all maintenance,
Memory management separates the on-board
On-board memory includes 64 K bytes of Read Only
with an administration terminal, a maintenance
The network controller transmits control channel
All uplink messages from the port circuits are checked for consistency and passed to the common control. The controller is the distribution control point for all downlink control messages.
the port circuit microprocessors for sanity and activity. External RAM
associated with this microprocessor stores control channel information and port related information.
The controller consists of bus buffers and a System And Control Interface (SAKI). The bus buffers provide the interface between the TDM bus and the on-board data buses to the SAKI. The SAKI receives and transmits control messages on the first five time slots on the TDM bus. The microprocessor communicates with the SAKI and external RAM over the address and data bus.
3-12
It continuously scans, over the TDM bus,
SYSTEM HARDWARE
Clock: A clock provides time of day information in seconds, minutes, and hours and the date to the 68010 microprocessor. The clock automatically adjusts for leap years. An on-board battery backs up the clock so that accurate time is maintained even when the system power is off.
Frontplane Interface: Dedicated buffers provide an interface to the
frontplane, which is the communication path to the Memory circuit pack. Reset Circuitry: The processor is automatically reset when power is turned
on, when the +5 volt power supply drops below 4.5 volts (after it returns to
+5 volts), or when the network controller detects the processor insane. The processor can also reset the network controller when it detects the network controller insane.
Bus Error Circuitry: Bus errors suspend the processor from executing code. Bus errors are generated when memory management detects illegal reads or writes to RAM, when the processor attempts to access circuit packs or chips not physically present, or when the network controller detects the processor insane.
Interrupt Circuitry:
Interrupts are prioritized into seven levels, of which the
highest (level 7) is non-maskable. The interrupts are:
Interrupt
AC Fail Work cycle Off board Two EIA ports Other two EIA ports Off board Off board
Level
7 6 5 4 3 2
1
Emergency Transfer Unit (ETU) Control: Removes -48 V dc power from the
system’s ETUs when the system loses power or a major system malfunction
occurs.
3-13
SYSTEM HARDWARE
Memory Circuit Pack [ZTN81 (V1) or ZTN127 (V2)]
The Memory circuit pack provides for the storage of software associated with system operation. and other related programs. The circuit pack is powered from the backplane by +5 volts. Memory circuit pack circuitry (Figure 3-6) includes:
Address and data buffers
ROM array
ROM select
Timing and control logic
Built-in TDM bus termination resistors.
This software includes call and administration processing
Each system must include one Memory circuit pack. The
Address and Data Buffers:
The address and data buffers interface the
Memory circuit pack to the address and data lines on the frontplane.
ROM Array: The memory array consists of 16 ROM devices of 32 K, 8-bit
bytes each, for a total capacity of 512 K ROM. The ROMs are organized into pairs allowing the Call Processor to access 16-bit words.
ROM Select: The memory selects the proper pair of ROMs according to address information.
Timing and Control Logic:
This circuit controls the access speed of the ROM (no wait states) by returning a Data Transfer Acknowledge signal at the proper time.
Termination Resistors: These resistors are required for proper operation of
the TDM bus. The ZTN81 (V1) or ZTN127 (V2) provides the proper termination for one end of the bus, and a plug-in TDM bus termination circuit
card (plugs into cabinet backplane) is used to terminate the other end. For
this reason, the ZTN81 (V1) or ZTN127 (V2) CP must always be located in
slot #1 of Cabinet 1.
3-14
I
SYSTEM HARDWARE
FRONT PANEL
MEMORY BUS
(TO CALL
PROCESSOR
CIRCUIT
PACK )
Figure 3-6.
TERMINATOR
RESISTORS
ARRAY
ADDRESS
AND
DATA BUFFERS
ROM
SELECT
TIMING
AND
CONTROL
Memory [ZTN81 (V1) or ZTN127 (V2)] Circuitry
ROM
TO TDM BUS
3-15
SYSTEM HARDWARE

Switching Network

System 25 uses distributed processing techniques to provide switched voice and data services. The switch operates at 64 Kbps. The switching network consists of the following:
Time Division Multiplex (TDM) bus
Port Circuits
System Resources.
The TDM bus connects the intelligent ports to the Common Control circuit
packs and other ports through the network control circuit. The system resource circuits provide tone sources, modems. The intelligent ports connect external communications facilities to
the TDM bus.
TDM Bus
The TDM bus consists of two groups of eight signal leads and five control leads, each with matching grounds. voice [pulse code modulated (PCM)] signals on the bus.
The bus operates at 2.048 MHz. The system framing pulse is 8 kHz. This
provides 256 time slots (0-255) on the bus. The time slots are 488 ns wide.
Time slots are generated as shown in Figure 3-7. The first five time slots are
used for communications between the Common Control, the intelligent port, and resource circuit packs. conversation.
Each party transmits (talks) on one time slot and receives
Two time slots are required for each 2-party
(listens) on another. Only five parties are allowed in a conference. During a conference connection, each member of the conference transmits on an individual time slot while receiving on as many as four other time slots. The actual switch capacity is 115 simultaneous 2-party conversations.
receivers, detectors, and pooled
The port circuit packs place digitized
Table 3-A shows the allocation of the 256 time slots. Five are used for system control, 15 for tones, 235 for call processing, and 1 is not used.
3-16
SYSTEM FRAME
8 KHZ
SYSTEM HARDWARE
(125 MICROSECONDS)
SYSTEM CLOCK
2.048 MHZ TIME SLOTS O
Figure 3-7.
488 NANOSECONDS
2
1
3
4 5
256 TIME SLOTS
_______
255 0
TDM Bus Time Slot Generation (Not a Timing Diagram)
I
3-17
SYSTEM HARDWARE
Table 3-A.
TIME SLOT NO.
00
thru
04
05
06 07 08 09 10 11 12 13 14
15
16
17 18 19
20
thru
254
TDM Bus Time Slots
FUNCTION
Control (5)
-Tones-(15)
Dial Tone Busy Tone Reorder Tone Ringback Tone
Data-Null Voice-Null Music 697 Hz* 770 Hz* 852 Hz* 941 Hz* 1209 Hz* 1336 Hz* 1447 Hz* 1637 Hz*
Call
Processing
(235)
255
Not Used
(1)
* These tones are used to generate touch-tone signals.
3-18
SYSTEM HARDWARE
Physical Characteristics:
The TDM bus is an 8-bit bus. The bus snakes continuously between cabinets in a multicabinet system as shown in Figure 3-8. The total length is about 9 feet for a 3-cabinet system. The bus is driven from any of the circuit packs in the cabinets. Similarly, a signal on the
bus can be received by any circuit pack.
Within a cabinet, the bus is printed on one side of the circuit pack carrier backplane, and the other side is solid ground. Ribbon cables are used to cable the TDM bus between cabinets in a multicabinet system.
Electrical Characteristics: The TDM bus is an unbalanced, low-characteristic
impedance transmission line. Paths printed over a ground plane on the carriers and the flat ribbon cables between carriers maintain this impedance level over the full length of the bus.
One end of the bus is terminated to ground with a bus termination circuit card and the other end is terminated by a network on the ZTN81 (V1) or ZTN127 (V2) Memory CP. Each circuit pack connects to the bus through a custom
bus driver device. The bus driver is a switchable constant current source so
that even in the “high”
output state there is no bus loading to cause reflections. The current output of the drivers is adjusted so that logic “high” is 1.5 volts compared to a “low” of 0 volts.
3-19
SYSTEM HARDWARE
TDM BUS TERMINATOR
CARD
TDM BUS EXTENDER CABLE
CABINET 3
ON/OFF SWITCH
AC POWER
# 6 AWG BUILDING GROUND WIRE
CABINET 2
AC POWER
Figure 3-8.
3-20
TO SINGLE
POINT GROUND
TDM Bus DIagram—3-Cabinet System
COUPLED BONDING CONDUCTOR (CBC)
AC POWER
#6 AWG GROUND WIRE
CABINET
1
SYSTEM HARDWARE
Port Circuits
The following port circuit packs provide the link between trunks and external equipment and the TDM bus:
Ground Start Trunk (ZTN76)
Loop Start Trunk (ZTN77)
Tip Ring Line (ZTN78).
ATL Line (ZTN79)
Data Line (TN726)
MET Line (TN735)
Analog Line (TN742)
DID Trunk (TN753)
Tie Trunk (TN760B)
Auxiliary Trunk (TN763)
STARLAN Interface (ZTN84) (V2)
Figure 3-9 shows the equipment types that can be connected to the digital switch by the Call Processor and port circuit packs. Figure 3-9 shows only overall concepts.
Some arrangements require auxiliary power and/or adapters. See the Installation and Test Manual (555-520-100) or Reference Manual (555-520-200) for complete details.
3-21
SYSTEM HARDWARE
SINGLE-LINE VOICE
TERMINALS
(420, 500, 2500, 2514,
2554, 7101A)
_ _ _ _ _ _ _ _
RECORDED ANNOUNCEMENTS — — — — — — — —
DICTATION EQUIPMENT
_ _ _ _ _ _ _ _
EXTERNAL ALERTING DEVICES
_ _ _ _ _ _ _ _
MUSIC-ON-HOLD
MULTILINE VOICE
TERMINALS (7300H-TYPE)
_ _ _ _ _ _ _ _
DIRECT TRUNK ATTENDANT
CONSOLE (7305H02B) OR SWITCHED LOOP ATTENDANT CONSOLE (7305H04C)
_ _ _ _ _ _ _ _
ATTENDANT DIRECT
EXTENSION SELECTOR CONSOLE
(MODEL 23A1)
PART OF DIGITAL SWITCH
ZTN78
TIP RING
LINE CP
OR
TN742
ANALOG
LINE CP
ZTN79
ATL LINE CP
DIVISION
MULTIPLEX
TIME
BUS
DICTATION EQUIPMENT
_ _ _ _ _ _ _ _
PAGING EQUIPMENT
(PagePac)
Figure 3-9.
3-22
MET SETS
NETWORK EXTENSION UNIT
TN735
MET LINE CP
TN763
AUXILIARY
TRUNK CP
ZTN84
STARLAN
INTERFACE
CP
Equipment Connected to System 25 By Call Processor and Port Circuit Packs (Sheet 1 of 3)
SAT, DTU, SMDR,
CAS (ON-PREMISES
DIRECT CONNECTION)
*REQUIRED FOR CONNECTIONS >50 FEET
OR NOT SHARING SAME AC OUTLET
Z3A1
ADU
*
Z3A4
ADU
*
_ _ _ _ _ _ _ _ _ _ _ _
SAT, SMDR,
CAS (ON-PREMISES
SWITCHED CONNECTION)
Z3A1/4
ADU
Z3A4
ADU
SYSTEM HARDWARE
PART OF DIGITAL SWITCH ZTN82 OR
ZTN128 PROCESSOR CP (1) SAT (2) SNDR, CAS (3) DTU (4) RESERVED
TN726
DATA LINE CP
TN726
DATA LINE CP
_ _ _ _ _ _ _ _ _ _ _ _
SAT, SMDR,
CAS (OFF-PREMISES)
DIRECT CONNECTION)
MODEM
(212-TYPE)
CO
MODEM
(212-TYPE)
_ _ _ _ _ _ _ _ _ _ _ _
SAT, SMDR,
CAS (OFF-PREMISES
SWITCHED CONNECTION)†
MODEM
(212-TYPE)
†OFF-PREMISES STATION
OR CO TRUNK
CO
OPS
OR
CO
Z3A4
ADU
ZTN82 OR
ZTN128 CALL
PROCESSOR CP
ZTN82 OR
ZTN128 CALL
PROCESSOR CP
TN742
ANALOG LINE CP
ZTN76 GROUND
START TRUNK CP OR ZTN77
LOOP START
TRUNK CP
TN726
DATE LINE CP
ZTN82 OR
ZTN128 CALL
PROCESSOR CP
TIME
DIVISION
MULTIPLEX
BUS
Figure 3-9.
Equipment Connected to System 25 By the Call Processor
and Port Circuit Packs (Sheet 2 of 3)
3-23
SYSTEM HARDWARE
DATA TERMINAL
EQUIPMENT,
HOST COMPUTER
SINGLE-LINE VOICE TERMINAL
(2500-TYPE OR
7101A)
DATA TERMINAL EQUIPMENT, HOST COMPUTER
MULTILINE
VOICE TERMINAL
(7300H-TYPE)
CO, FX, WATS
_ _ _ _ _
PAGING EQUIPMENT
DID TRUNKS
RS-232C
RS-232C
Z3A1/2/4
ADU
Z3A5
ADU
PART OF DIGITAL SWITCH
TN726
DATA LINE CP
TN742
ANALOG LINE
CP OR ZTN78 TIP
RING LINE CP
TN726
DATA LINE CP
ZTN79
ATL LINE CP
ZTN76
GROUND START
TRUNK CP
OR
ZTN77
LOOP START
TRUNK CP
TN753
DID
TRUNK CP
DIVISION
MULTIPLEX
TIME
BUS
TIE TRUNKS
LEGEND:
ADU – CAS -
CO -
CP ­DID ­DTU –
FX -
MET – OPS -
SAT – SMDR ­WATS -
Figure 3-9.
3-24
TN760B
TIE
TRUNK CP
ASYNCHRONOUS DATA UNIT CALL ACCOUNTING SYSTEM CENTRAL OFFICE CIRCUIT PACK DIRECT INWARD DIALING DIGITAL TAPE UNIT FOREIGN EXCHANGE MULTIBUTTON ELECTRONIC TELEPHONE OFF-PREMISES STATION SYSTEM ADMINISTRATION TERMINAL STATION MESSAGE DETAIL RECORDING WIDE AREA TELECOMMUNICATIONS SERVICE
Equipment Connected to System 25 By the Call Processor
and Port Circuit Packs (Sheet 3 of 3)
SYSTEM HARDWARE
Eight port circuits are provided on most port circuit packs. The MET Line, Tie Trunk, and Auxiliary Trunk CPs each contain four port circuits. The port circuits provide an interface between terminals/trunks and the TDM bus. The STARLAN Interface CP (V2) is unique.
It provides one interface (port) to a
Network Extension Unit (NEU) and four connections to the TDM bus.
The number of port circuit packs required varies per customer requirements and equipment configuration.
Each of the System 25 port circuit packs contain a number of common
elements (see Figure 3-10), such as:
Bus buffers
Sanity And Control Interface (SAKI)
On-board microprocessor with external Random Access Memory (RAM)
One or more Network Processing Elements (NPEs)
Circuit Pack Address Leads.
3-25
SYSTEM HARDWARE
TDM BUS LEADS
CIRCUIT PACK ADDRESS
LEADS
Figure 3-10.
BUS
BUFFERS
LEDS
SAKI
RED GREEN YELLOW
NPE(S)
Port Circuit Pack Common Circuitry
RAM
ON-BOARD
MICRO-
PROCESSOR
PORT
SPECIFIC CIRCUITRY
3-26
SYSTEM HARDWARE
BUS Buffers: The bus buffers are the digital interface between the backplane TDM bus wires (system bus) and the on-board circuitry (data bus). They also
receive and distribute clock and frame signals.
SAKI (Sanity And Control Interface):
The SAKI is the control interface
between the Common Control that sends information via the network control circuit down the TDM buses and the on-board circuitry controlled by the on­board microprocessor.
The SAKI receives control information (down-link messages) on the first five time slots and, as requested by the on-board microprocessor, transmits control information (up-link messages) on these same time slots.
The SAKI also performs the following functions:
Identifies the circuit pack to the Common Control (location and vintage)
Controls status indicator light-emitting diodes (LEDs)—red (failure), green
(translated), and yellow (circuit busy)
Initiates power-on startup procedures
Checks the on-board microprocessor for sanity and causes reinitialization
if problems occur
Takes NPEs out of service under control of the on-board microprocessor
Resets the protocol handler on the ATL Line circuit pack
Generates the STARLAN NETWORK address on the STARLAN Interface
circuit pack
Resets the OATMEAL devices on the STARLAN Interface circuit pack
Takes the whole circuit pack out of service on command from the
Common Control or when it determines that on-board interference is present in the control time slots.
On-Board Microprocessor With External RAM: The on-board processor performs all low level functions such as scanning for changes and relay operations. In general, it carries out commands received from the Common Control and reports status changes to it. The on-board processor also
provides a Tier 3 maintenance interface to an RS-232C asynchronous terminal on the STARLAN Interface circuit pack. The external RAM stores control channel information and port-related information.
3-27
SYSTEM HARDWARE
NPEs (Network Processing Element): Each port circuit pack contains one or two NPEs. The Analog Line, ATL Line, Tip Ring Line, Data Line, Ground Start, Loop Start, and DID Trunk circuit packs contain two NPEs. The MET Line, Auxiliary Trunk, and Tie Trunk circuit packs contain one NPE.
The NPEs perform switching network functions for the port circuits. Under control of the on-board microprocessor, an NPE can connect a port circuit to
any one of the TDM bus time slots.
More specifically, it allows a port circuit to talk on one time slot and listen to the same time slot (NPE sidetone) and on up to four other time slots at the same time.
In 2-wire circuits that provide
their own sidetone, the NPE sidetone is not used.
Circuit Pack Address Leads:
Seven leads (BA0-BA6) are tied to corresponding logic levels to uniquely identify each CP slot in the system, including multiple cabinet systems.
The logic values on leads BA4 and BA5 are used to identify the cabinet (Cabinet 1, 2, or 3) and are tied by the cabinet address plugs to either +5 V dc or ground, as appropriate. Lead BA6 is tied to ground.
3-28
SYSTEM HARDWARE
Ground Start Trunk (ZTN76)
The Ground Start Trunk circuit pack interfaces eight central office trunks and the TDM bus. Figure 3-11 shows the following Ground Start Trunk unique circuitry:
Ground detector circuit
Port Input/Output (I/O) circuit
Eight port circuits.
Ground Detector Circuit: The ground detector circuit determines if ground
has been applied to the tip lead for incoming seizure. It also senses tip ground on outgoing seizure indicating dial tone is present. One ground sensor is used for each port circuit. Input for the ground sensor comes from the port circuit as an analog current to the -48 V dc supply. The ground sensor’s output is a port control point to the port I/O circuit.
Port I/O Circuit: This circuit consists of bus expanders for communication
between the on-board microprocessor and the port circuits. It receives commands from the on-board microprocessor and distributes them to the individual port circuits.
It also accesses the port circuit scan points and
passes the information to the on-board microprocessor.
Port Circuits: The eight port circuits are identical. Each port circuit consists of a coder/decoder (codec), hybrid circuit, line transformer, relay driver, and surge protection circuit.
The codec is a 4-wire circuit that converts the NPEs digital output to an analog signal.
Likewise, it converts the analog signal from a central office
trunk to a Pulse Code Modulation (PCM) data signal to the NPE. The hybrid
circuit converts the codec 4-wire analog signal to a 2-wire analog signal that is connected to the central office trunk by the line transformer.
The relay driver buffers and inverts the relay drive signals from the port I/O circuit so that a logic high input operates the appropriate relay. The relay control circuitry provides the proper signaling for ground start trunks. The trunks support touch-tone dialing.
The surge protection circuit provides
overvoltage lightning surge protection for the circuit pack.
3-29
SYSTEM HARDWARE
NPE O
NPE 1
PORT CIRCUIT
CODEC
0
HYBRID
T.O
R.O
ON-BOARD MICRO­PROCESSOR
Figure 3-11.
3-30
PORT
PORT
I/O
CIRCUIT
GROUND
DETECTOR
CIRCUIT
3
PORT
CIRCUIT
4
PORT
CIRCUIT
7
Unique Ground Start Trunk (ZTN76) Circuitry
T.3
R.3
T.4
T.7
R.7
TO CENTRAL OFFICE
SYSTEM HARDWARE
Loop Start Trunk (ZTN77)
The Loop Start Trunk circuit pack interfaces eight central office loop start trunks and the TDM bus. Figure 3-12 shows the following Loop Start Trunk
unique circuitry:
Port Input/Output (I/O) circuit
Eight port circuits.
Port I/O Circuit:
This circuit consists of bus expanders for communication between the on-board microprocessor and the port circuits. It receives commands from the on-board microprocessor and distributes them to the individual port circuits.
It also accesses the port circuit scan points and
passes the information to the on-board microprocessor. Port Circuits: The eight port circuits are identical. Each port circuit consists
of a codec, hybrid circuit, line transformer, relay driver, and surge protection circuit.
The codec is a 4-wire circuit that converts the NPEs output to an analog signal. Likewise, it converts the analog signal from a central office trunk to a PCM data signal to the NPE. The hybrid circuit converts the codec 4-wire analog signal to a 2-wire analog signal that is connected to the central office
trunk by the line transformer. The relay driver buffers and inverts the relay drive signals from the port I/O
circuit so that a logic high input operates the appropriate relay. The relay control circuitry provides the proper signaling for loop start trunks. The trunks support touch-tone dialing and dial pulse signaling. The surge protection circuit provides overvoltage lightning surge protection for the circuit pack.
3-31
SYSTEM HARDWARE
NPE O
NPE 1
PORT CIRCUIT
CODEC
0
HYBRID
T.O
R.O
ON-BOARD MICRO­PROCESSOR
Figure 3-12.
3-32
PORT
PORT
I/O
CIRCUIT
CIRCUIT
3
PORT
CIRCUIT
4
PORT
CIRCUIT
7
Unique Loop Start Trunk (ZTN77) Circuitry
T.3
R.3
T.4
R.4
T.7
R.7
TO CENTRAL OFFICE
SYSTEM HARDWARE
Tip Ring Line (ZTN78)
The Tip Ring Line circuit pack interfaces eight analog tip and ring voice terminal lines (single-line voice terminals) and the TDM bus. Figure 3-13 shows the following Tip and Ring Line unique circuitry:
Ringing application circuit
Port Input/Output (I/O) circuit
–48 V to -24 V Power Conditioner
Eight port circuits.
Ringing Application Circuit:
This circuit receives ringing voltage from the
power supply. It monitors ringing voltage and current and generates signals to the on-board microprocessor indicating zero ringing voltage and current. It also detects when a terminal user has lifted the receiver during ringing,
preventing the application of ringing to the terminal’s handset receiver. Port I/O Circuit: This circuit includes bus expanders connecting the on-board
microprocessor and the port circuits.
It receives commands from the on­board microprocessor and distributes them to the individual port circuits. It also accesses the port circuit scan points and passes the information to the on-board microprocessor.
-48 V To -24 V Power Conditioner: This circuit converts -48 V power from the power supply into a conditioned source of -24 V power for the electronic
battery feed circuits.
Port Circuits:
Each port circuit is identical. A port circuit consists of a
coder/decoder (codec), hybrid circuit, battery feed circuit, and ring relay. The codec is a 4-wire circuit that converts the NPE’s output to an analog
signal. Likewise, it converts the analog signal from a central office trunk to a PCM data signal to the NPE. The hybrid circuit converts the codec 4-wire
analog signal to a 2-wire analog signal that is connected to the central office trunk by the line transformer.
The battery feed circuit provides talking battery to the voice terminal. It also detects when a receiver is lifted, and provides the message waiting signal by periodically reducing the feed voltage to zero.
The ring relay provides the interface between the ringing application circuit and the port circuit. It causes ringing to turn on and off.
3-33
SYSTEM HARDWARE
PORT
CIRCUIT
0
NPE O
NPE 1
ON-BOARD MICRO­PROCESSOR
POWER SUPPLY
Figure 3-13.
CODEC
PORT
I/O
CIRCUIT
RINGING
APPLICATION
CIRCUIT
-48V TO -24V POWER
CONDITIONER
HYBRID
Unique Tip Ring Line (ZTN78) Circuitry
PORT
CIRCUIT
3
PORT
CIRCUIT
4
PORT
CIRCUIT
7
ELECTRONIC
BATTERY
FEED
T.O
R.O
T.3
R.3
T.4
R.4
T.7
R.7
TO
ANALOG
TIP/RING
VOICE
TERMINALS
3-34
SYSTEM HARDWARE
ATL Line (ZTN79)
The ATL Line circuit pack interfaces eight hybrid voice terminal (7300H
series) lines and the TDM bus. It terminates three pairs of wires from each terminal: analog voice pair, digital control pair, and power pair. Figure 3-14 shows the following ATL Line unique circuitry:
Protocol handler
Eight port circuits.
Protocol Handler: The 8-bit on-board microprocessor translates the control
information in CCMS message format to the control information message
format used by the 7300H series voice terminals. The protocol handler sends the messages to the terminals using transceivers located in the port circuits.
Port Circuits: Each port circuit is identical. A port circuit consists of an analog port, one-half of a transceiver, and an electronic power feed device.
The analog port circuit consists of a codec, a hybrid circuit, an isolation
transformer, and associated power filtering circuitry. The codec and hybrid
circuits perform the same function as the codec and hybrid circuits in the Analog Line circuit pack (TN742).
The output of the hybrid circuit is
connected to the primary of the isolation transformer. The secondary of the
transformer is connected to the analog voice pair. The transceiver interfaces the voice terminal pair to the protocol handler.
The electronic power feed device provides -48 V dc on the power pair to the voice terminal. The device is polled by the on-board microprocessor, periodically and on demand,
to test for an overcurrent or no-current
condition. Each Electronic Power Feed (EPF) circuit supports two ports. If one of the
associated lines become overloaded, the associated pair of lines will also be out of service. One EPF supports Ports 0 and 1, one supports Ports 2 and 3, one supports Ports 4 and 5, and one supports Ports 6 and 7. The on/off state of the device is controlled by the on-board microprocessor.
3-35
SYSTEM HARDWARE
NPE O
ON-BOARD MICRO­PROCESSOR
ON-BOARD MICRO­PROCESSOR
NPE 1
PROTOCOL
HANDLER
PORT CIRCUIT PORT O
ANALOG PORT
CODEC
HYBRID
TRANSCEIVER
ELECTRONIC POWER FEED
CIRCUIT
CIRCUIT
PORT
CIRCUIT
DATA
PORT
3
PORT
4
7
ISOLATION
TRANSFORMER
T.0 R.0
TXT.O TXR.O
PXT.0 PXR.0
PXT.1 PXR.1 T.3
R.3 TXT.3 TXR.3 PXT.3 PXR.3
T.4 R.4
TXT.4
TXR.4
PXT.4 PXR.4
T.7 R.7 TXT.7 TXR.7
PXT.7 PXR.7
TO MULTILINE VOICE TERMINALS
Figure 3-14.
3-36
Unique ATL Line (ZTN79) Circuitry
SYSTEM HARDWARE
Data Line (TN726)
The Data Line circuit pack interfaces eight Asynchronous Data Units (ADUs) data devices and the TDM bus. The ADUs are typically, in turn, connected to
RS-232C-type devices.
Figure 3-15 shows the Data Line unique circuitry that
includes:
A bit clock
Bus isolation
Eight port circuits.
Bit Clock: The bit clock circuitry is used to provide the OATMEALs (Octal Asynchronous Terminal Mode Two EIA Asynchronous LSIs) with a clock frequency that is a multiple of each baud rate. In addition, the clock rate is divided down to 160 kHz. The 160 kHz is then compared to the system’s 160
kHz data clock and is phase-locked to the system clock. The phase-locked
circuit is required for low-speed operation.
Bus Isolation:
This portion of the circuit pack is used to isolate the microprocessor bus. Isolation is required because the realized bus load exceeds the maximum limit specified for this device, due to the large number of devices controlled by the NPE. The OATMEALs are isolated from the common bus structure.
Port Circuits: Each of the eight identical port circuits allows the connection of interface equipment having an RS-232C compatible serial interface to the switch. The circuit provides an asynchronous full-duplex subset of standard data speeds from 300 to 19,200 bps. Each port includes an Asynchronous Data Unit (ADU) to extend the serial communications link length and provide safe isolation. The ADU terminates to another ADU at the Customer­Provided Equipment (CPE). The distance between the digital switch and CPE is inversely proportional to the speed at which the link is run. See Reference
Manual (555-520-200) for details. Throughout the circuit, various gates are used to provide a means of isolating
devices for automated circuit pack testing. Typically, these devices are crystal oscillators or memory components attached to the microprocessor bus.
3-37
SYSTEM HARDWARE
NPE
0
ON-BOARD
MICROPROCESSOR
NPE
1
BUS ISOLATION
BIT
CLOCK
A
A
A
A
A
A
A
A
PORT CIRCUIT O
PROTOCOL
HANDLER
(OATMEAL)
ASYNCHRONOUS
DATA UNIT (ADU)
PORT
CIRCUIT
1
PORT
CIRCUIT
2
PORT
CIRCUIT
3
PORT
CIRCUIT
4
PORT
CIRCUIT
5
PORT
CIRCUIT
6
PORT
CIRCUIT
7
PXT.0 PXR.0 TXT.0 TXR.0
I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I
PXT.7 PXR.7 TXT.7 TXR.7
TO ADUS
Figure 3-15.
3-38
Unique Data Line (TN726) Circuitry
SYSTEM HARDWARE
MET Line (7N735)
The MET Line circuit pack interfaces four Multibutton Electronic Telephone (MET) lines and the TDM bus. The MET Line unique circuitry consists of four port circuits as shown in Figure 3-16.
Port Circuits: The four port circuits are identical. Each port circuit consists
of an analog port, a digital port, and an electronic power feed device.
The analog port circuit consists of a codec, a hybrid circuit, an electronic
battery feed, and a power filter.
The codec, hybrid circuit, and power filter perform the same function as in the Analog Line circuit pack (TN742). The electronic battery feed provides talking battery to the MET set. The electronic battery feed produces a controlled dc battery feed current for short and long loops and detects when a MET set user lifts a receiver.
The digital port circuit provides a full-duplex channel over two 2-wire pairs. All outgoing lamp (LT, LR) and incoming button depression (BT, BR) information is carried on these channels. Ringing and switchhook information is also sent over these channels.
The electronic power feed device provides phantomed -48 V dc power for the MET terminals over the data channels. The electronic power feed device
is a
“smart” circuit breaker. When it senses an overcurrent condition, it indicates the condition on an output lead and goes into thermal shutdown if not turned off by the on-board microprocessor. When the overcurrent condition disappears, the circuit breaker can be turned on by the on-board microprocessor.
3-39
SYSTEM HARDWARE
PORT CIRCUIT
ON-BOARD
MICRO-
PROCESSOR
Figure 3-16.
NPE
ANALOG
PORT
DIGITAL
PORT
ELECTRONIC POWER FEED
PORT CIRCUIT
Unique MET Line (TN735) Circuitry
T.O R.O
BT.O
BR.O
LT.O LR.O
TO MET
TERMINALS
T.3 R.3 BT.3
3
BR.3 LT.3 LR.3
3-40
SYSTEM HARDWARE
Analog Line (lN742)
The Analog Line circuit pack interfaces eight analog voice terminal lines and the TDM bus. Figure 3-17 shows the following Analog Line unique circuitry:
Ringing application circuit
Port Input/Output (I/O) circuit
Eight port circuits.
Ringing Application Circuit:
This circuit receives ringing voltage from the
power supply. It monitors ringing voltage and current, generates signals to
the on-board microprocessor indicating zero ringing voltage and current, and
detects a terminal user lifting the receiver during ringing. This prevents the application of ringing to the port circuit when a terminal user lifts the receiver during the ringing phase.
Maintenance circuitry is also included. The maintenance circuitry detects when a terminal is connected to the port circuitry and checks for faults in the ringing application circuitry.
Port I/O Circuit: This circuit consists of bus expanders connecting the on­board microprocessor and the port circuits. It receives commands from the on-board microprocessor and distributes them to the individual port circuits. It also accesses the port circuit scan points and passes the information to the on-board microprocessor.
Port Circuits: The eight port circuits are identical. Each port circuit consists of a coder/decoder (codec), hybrid circuit, electronic battery feed circuit, ring relay, and overvoltage surge protection circuit.
The codec is a 4-wire circuit that converts the analog signal from a voice
terminal to a PCM data signal. It converts an incoming PCM data signal from the NPEs to an analog signal. The hybrid circuit converts the 4-wire analog signal from the codec to a 2-wire analog signal that is connected to the analog line. Filtered power is provided for the codec and hybrid circuits.
The electronic battery feed circuit provides talking battery to the voice terminal. It also produces a controlled dc battery feed for short and long
loops, detects when a receiver is lifted, and provides the message waiting signal by periodically turning off the feed voltage.
The ring relay provides the interface between the ringing application circuit and the port circuit. It causes ringing turn on and turn off.
The overvoltage surge protection circuit provides lightning surge and power line cross protection for the circuit pack.
3-41
SYSTEM HARDWARE
Note:
The TN742 may be used instead of the ZTN78 Tip Ring circuit pack. The TN742 supports up to five bridged single-line voice terminals; however, only two may be off-hook at one time. The ZTN78 circuit pack does not support bridged terminals. In addition, the TN742 supports out-of-building, extended, and off-premises stations; the ZTN78 does not.
PORT CIRCUIT
0
NPE 0
NPE 1
ON-BOARD MICRO­PROCESSOR
POWER SUPPLY
PORT
I/O
CIRCUIT
RINGING
APPLICATION
CIRCUIT
CODEC
HYBRID
PORT
CIRCUIT
PORT
CIRCUIT
PORT
CIRCUIT
ELECTRONIC
OVERVOLTAGE
PROTECTION
I I I
I
I
3
4
I I
I
7
BATTERY
FEED
T.0
R.0
T.3
R.3
T.4
R.4
T.7
R.7
TO ANALOG TIP/RING VOICE TERMINALS
Figure 3-17.
3-42
Unique Analog Line (TN742) Circuitry
SYSTEM HARDWARE
DID Trunk (TN753)
The DID Trunk circuit pack interfaces eight central office trunks arranged for
Direct Inward Dialing (DID) and the TDM bus. Figure 3-18 shows the
following DID Trunk unique circuitry:
Port Input/Output (I/O) circuit
Eight port circuits.
Port I/O Circuit: This circuit consists of bus expanders for communication
between the on-board microprocessor and the port circuits. It receives commands from the on-board microprocessor and distributes them to the individual port circuits.
It also accesses the port circuit scan points and
passes the information to the on-board microprocessor.
Port Circuits: The eight port circuits are identical. Each port circuit consists of a codec, balance network, trunk interface unit, and loop termination circuit.
The codec is a 4-wire circuit that converts the NPE output to an analog signal. Likewise, it converts the analog signal from the central office (CO) to a PCM signal to the NPE.
The trunk interface unit contains a hybrid circuit, a 2-wire interface circuit,
and control circuitry.
The hybrid circuit converts the 4-wire analog signal from the codec to a 2-wire analog signal that is connected to the analog line by the 2-wire interface circuit.
The control circuitry controls loop current, internal signal gain, terminating resistance, battery feed shutdown, and battery reversal.
The circuit pack accepts both dial pulse and touch-tone
signaling.
The loop termination circuit provides a fixed impedance to the DID trunk.
3-43
SYSTEM HARDWARE
NPE 0
NPE 1
PORT CIRCUIT
CODEC
0
INTERFACE
TRUNK
UNIT
HYBRID
T.O
R.0
ON-BOARD MICRO-
PROCESSOR
Figure 3-18.
PORT
CIRCUIT
3
PORT
I/O
CIRCUIT
PORT
CIRCUIT
4
PORT
CIRCUIT
7
Unique DID Trunk (TN753) Circuitry
T.3
R.3
T.4
R.4
T.7
R.7
TO CENTRAL OFFICE
3-44
SYSTEM HARDWARE
Tie Trunk (TN760B)
The Tie Trunk circuit pack interfaces four 6-wire tie trunks and the TDM bus. Two tip and ring pairs form a 4-wire analog transmission line. An E and M pair is used for signaling. The T and R pair transmits analog signals from the
circuit pack. The T1 and R1 pair receives analog signals from the tie trunk. The E and M pair are dc signaling leads used for call setup handshaking. The E lead receives signals from the tie trunk and the M lead provides signals from the circuit pack. The TN760B’s four port circuits support Type I, Type I Compatible, or Type V signaling.
Incoming and outgoing trunks may be either automatic, immediate start, wink start, or delay dial. Figure 3-19 shows the following Tie Trunk unique circuitry:
Ground detector circuit
Port Input/Output (I/O) circuit
Four port circuits.
Ground Detector Circuit: This circuit determines if a ground has been
applied to the E lead. Ground detector inputs come from the port circuits as
an analog current to the -48 V dc supply. Its output is a port control point to the port I/O circuit.
Port I/O Circuit: This circuit consists of bus expanders for communication between the on-board microprocessor and the port circuits. It receives commands from the on-board microprocessor and distributes them to the individual port circuits.
It also accesses the port circuit scan points and
passes the information to the on-board microprocessor.
Port Circuits: The port circuits are identical, except for port 3 where part of the E-lead maintenance circuit is located. Each port circuit consists of a codec with associated input and output line transformers, analog operational
amplifiers, a power filter, loop-around transistors, port control comparators, a relay driver, an electronic power feed device, an E-lead test maintenance
circuit, and surge protection circuits. The codec converts the incoming 4-wire analog signal from the tie trunk to a
PCM data signal. The codec converts the incoming PCM data signal from the NPE to an analog signal. provide dc isolation to the tip and ring leads.
Outgoing and incoming line transformers
Analog operational amplifiers provide amplification and buffering for the codec and network and loop­around gain compensation.
Filtered power is provided to the codec and
amplifiers.
3-45
SYSTEM HARDWARE
The loop-around transistors are under control of the port control comparators and provide a loop-around path for the signal for testing purposes. The relay
driver buffers and inverts the relay drive signals from the port I/O circuit so that a logic high input operates the appropriate relay. The relays and electronic power feed device control the M-lead circuitry to provide the
proper signaling handshake for call progress tones and dial pulse dialing. The electronic feed device provides a -48 V dc current to the M-lead circuits.
It also tests the M-lead circuits for opens or shorts and prevents uncontrolled operation during powerup. ground detector circuit for testing provides lightning surge and power
NPE
ON-BOARD MICRO­PROCESSOR
The E-lead test circuit provides a ground to the
purposes. The surge protection circuitry cross protection for the circuit pack.
T.0 R.0 T1.0 R1.0 E.0
M.0
PORT
I/O
CIRCUIT
PORT
CIRCUIT
0
T.3 R.3 T1.3 R1.3
E.3
M.3
TO TIE TRUNKS
Figure 3-19.
GROUND
DETECTOR
CIRCUIT
Unique Tie Trunk (TN760B) Circuitry
PORT
3
Various signaling formats (consists of a mode and a type) are available with the TN760B. The mode designates the electrical interface and the type designates the logical signaling used.
For each port circuit, the mode is selected by option switch settings on the CP. Table 3-B lists the preferred signaling formats for
option switch settings.
3-46
likely-to-be encountered installation situations and
The option switches are shown in Figure 3-20.
SYSTEM HARDWARE
Table 3-B.
Circumstance
Co-Located
Inter-Bldg.
Co-Located
Inter-Bldg.
Co-Located
Inter-Bldg.
Co-Located
TN760B Option Switch Settings and Administration
System 25
Installation
Situation
S25/S75
S25/S75
S85
S85
DIMENSION PBX
DIMENSION PBX
Other
To
Preferred
Signaling Format
System 25
Simplex Type 5
Simplex Type 5
Simplex Type 5
Simplex Type 5
E&M Type 1 Compatible
Prot. Type 1 Compatible
E&M Type 1 Compatible
Far-End
Simplex Type 5
Simplex Type 5
Simplex Type 5
Simplex Type 5
E&M Type 1 Standard
Prot. Type 1 Standard
E&M Type 1 Standard
Set
E&M/
SMPLX
Option Switch
SMPLX
SMPLX
SMPLX
SMPLX
E&M
E&M
E&M
Unprot Option Switch
Either
Either
Either
Either
Unprot
Prot
Unprot
Set
Prot/
Administer
the Port
Type 5
Type 5
Type 5
Type 5
Type 1 Compatible
Type 1 Compatible
Type 1 Compatible
Inter-Bldg.
Co-Located
Other
Net Int.
Prot. Type 1 Compatible
E&M Type 1 Standard
Prot. Type 1 Std. Plus Protection Unit
Don’t Care
E&M
E&M
Prot
Unprot
Type 1 Compatible
Type 1
3-47
SYSTEM HARDWARE
UNPROT.
PORT: 4 3 2 1
PROT.
Figure 3-20.
Tie Trunk (TN760B) Circuit Pack Option Switches
Table 3-C summarizes
control signals for each
Table 3-C.
Signaling Type Summary
SIGNALING
TYPE On-Hook Off-Hook
I Std.
I Compat.
V open
SMPLX
E&M
the conditions
signaling type.
TRANSMIT RECEIVE
grd bat open/bat (*) grd
open/bat (*) grd
SMPLX SMPLX
PORT 4 PORT 3 PORT2 PORT 1
E&M
grd
* An open circuit is preferred over voltage.
E&M
present
as the transmit and receive
On-Hook Off-Hook
grd
open
SMPLX
E&M
open/bat (*)
grd
3-48
SYSTEM HARDWARE
Auxiliary Trunk (TN763)
The Auxiliary Trunk circuit pack interfaces four ports provided for customer­provided equipment (CPE) and the TDM bus. It is connected to the CPE by up to three pairs of wires. signals and touch-tone control signals.
The transmission pair (T and R) carries voice
T and R also provides a loop start seizure indication to the CPE. The seizure pair (SZ and SZ1) provides seizure indication to the CPE. The signal pair (S and S1) provides answer supervision and/or make-busy information from the CPE. Depending on the
application, the transmission pair only or all three pairs are connected to the CPE.
Figure 3-21 shows the following Auxiliary Trunk unique circuitry:
Ground detector circuit
Port Input/Output (I/O) circuit
Four port circuits.
Ground Detector Circuit: This circuit determines if an answer-supervision or
make-busy signal from the CPE is present. The ground detector’s inputs
come from the port circuits as an analog current to the -48 volt dc supply.
Its output is a port control point to the port I/O circuit.
Port I/O Circuit:
This circuit consists of bus expanders for communication between the on-board microprocessor and the port circuits. It receives commands from the on-board microprocessor and distributes them to the individual port circuits.
It also accesses the port circuit scan points and
passes the information to the on-board microprocessor.
Port Circuits: The four port circuits are identical. Each port circuit consists of a codec, hybrid circuit,
line transformer, relay driver, battery polarity
sensor, and surge protection circuit.
The codec is a 4-wire circuit that converts the analog signal from the CPE to a PCM data signal. an analog signal.
It converts an incoming PCM data signal from the NPE to
The hybrid circuit converts the 4-wire analog signal from the codec to a 2-wire analog signal that is connected to the CPE by a line transformer.
The relay driver buffers and inverts the relay drive signals from the port I/O
circuit so that a logic high input operates the appropriate relay. The relay control circuitry provides the proper interfaces for CPE.
3-49
SYSTEM HARDWARE
The surge protection circuit provides lightning surge protection for the circuit
pack. Longitudinal surges are isolated from the hybrid and codec by the line
transformer.
T.0 R.0
S.0 S1.0 SZ.0
SZ1.0
TO AUXILIARY EQUIPMENT
NPE
ON-BOARD MICROPROCESSOR
PORT
CIRCUIT
0
PORT
I/O
CIRCUIT
Figure 3-21.
3-50
GROUND
DETECTOR
PORT
CIRCUIT
3
Unique Auxiliary Trunk (TN763) Circuitry
T.3 R.3 S.3
S1.3 SZ.3
SZ1.3
SYSTEM HARDWARE
System Resources
The System Resource circuit packs are as follows:
Service Circuit (ZTN85)
Tone Detector (TN748)
Pooled Modem (TN758).
Service Circuit (ZTN85)
The Service Circuit circuit pack provides the system’s clock signals. It also generates and receives tones.
The Service Circuit circuit pack (Figure 3-22)
consists of the following:
Bus buffers
Sanity And Control Interface (SAKI)
On-board microprocessor with external RAM
Clock circuit
Tone Generator
Time slot table and counter
Tone detector ports
Port I/O and Sanity Check circuit.
The ZTN85 provides four touch-tone receivers, generates all tones for the system, and supplies the system clocks. Dual Tone Multifrequency (DTMF) dialers.
The ZTN85 can support up to 75
Each System 25 must contain one
Service Circuit circuit pack. Power for the circuit pack (+5 V dc) is provided
on the backplane. Bus Buffers: There are four bus buffers on the circuit pack. The clock driver
and receive buffers interface three system clock signals (2.048 MHz, 8 kHz, and 160 kHz) to the TDM bus. Two buffers interface the system tones (see Table 3-A) between the TDM bus and the Service Circuit circuit pack. Music is not provided by the Service Circuit but may be provided by a port interface on a Tip Ring Line circuit pack (ZTN78).
SAKI: This circuit functions the same as in the SAKI in the common circuitry
for the intelligent port circuits.
3-51
SYSTEM HARDWARE
On-Board Microprocessor With External RAM: This circuit functions the same as the microprocessor in the common circuitry for the intelligent port
circuits. In addition, it tells the dual-port RAM in the time slot table circuit the
appropriate time slots in which to place a tone. The external RAM also has
work space for complex tones (that is, those tones that vary with time). Clock Circuit: The clock circuit consists of a 20.48-MHz oscillator, various
dividers, and shift registers.
The clock circuit runs independently from the rest of the Service Circuit circuitry. The clock circuits start running when the circuit pack is first powered up and is not controlled by the on-board microprocessor.
The output of the 20.48-MHz oscillator is fed to the clock divider. The divider divides by 10, 2560, and 128. These circuits produce the 2.048-MHz, 8-kHz, and 160-kHz clock signals, respectively.
The clock generator feeds these signals to the clock driver/receiver bus buffer and the tone clock. The tone clock uses these signals to synchronize the counters in the tone generator and time slot table circuits with the TDM bus.
Tone Generator: The tone generator consists of a digital signal processor (DSP), a counter, and a dual-port tone RAM. The DSP operates at 10 MHz and produces 24 different tones. The dual-port tone RAM stores these tones in 24 different addresses. The counter under control of the tone clock causes
the DSP to transmit one sample of each tone every 8 kHz. The counter is
synchronized to the TDM bus and is offset to provide delay needed for
access time. Time Slot Table and Counter: The time slot table consists of a dual-port time
slot table RAM and a counter. The dual-port RAM (DPRAM) contains 256 different addresses. These addresses correspond to the time slots on the TDM bus. The counter sequences through the time slot table addresses in the dual-port RAM and causes the proper tone(s) to be output by the dual­port tone RAM on TDM bus time slots.
Tone Detector Ports: The Service Circuit circuit pack provides four Dual­Tone Multifrequency (DTMF) detector port circuit interfaces via the TDM bus. Each port circuit is connected to an NPE serial input and output. Ports 0, 1, 2, and 3 are DTMF tone detectors with NPE loop-around paths.
The four port circuits contain a DSP, NPE to DSP interface circuitry, a DSP restart circuit, and an interrupt generator. One DSP implements two tone receivers.
The TDM bus signals are connected to the DSP in serial form from the NPEs by the DSP interface circuit.
The DSP controls the output clocking of the
NPE. The system framing signal is synchronized and connects to the DSP.
3-52
SYSTEM HARDWARE
Port I/O and Sanity Check Circuit:
This circuit interfaces the on-board
microprocessor to the port circuits and checks the sanity status of the port
circuits’ DSPs.
TONE
GENERATOR
(DSP)
TIME SLOT TABLE (DPRAM)
RAM
U-CONTROL
TDM BUS LEADS
CIRCUIT PACK ADDRESS LEADS
LEDs
BUS BUFFER
RED YELLOW
GREEN
TONE TABLE (DPRAM)
SAKI
NETWORK
BUS
ADDRESS & DATA BUS
Figure 3-22.
NPE
SYSTEM CLOCK
Service Circuit (ZTN85)
TONE DETECTORS
OUTPUT
REGISTERS
3-53
SYSTEM HARDWARE
Tone Detector (TN748)
The Tone Detector circuit pack provides four touch-tone receivers and two general purpose tone receivers that detect appropriate system and network tones on the TDM bus.
The Tone Detector circuit pack consists of the same common circuitry as the
intelligent port circuits and the following unique circuits (see Figure 3-23):
Port I/O circuit
Port and DSP Sanity check circuit
Four touch-tone port circuits
Two general purpose tone detector port circuits
Two NPE loop-around test port circuits.
Up to a maximum of two Tone Detector circuit packs may be provided in the system.
Port I/O and Sanity Check Circuit:
This circuit interfaces the on-board
microprocessor to the port circuits and checks the sanity status of the port
circuits Digital Signal Processors (DSPs). Port Circuits: There are eight port circuits.
Six port circuits are connected to
NPEs. Port circuits 0, 1, 4, and 5 are DTMF tone detector ports. Each of the
six port circuits has an associated DSP, NPE to DSP interface circuitry, a DSP restart circuit, and an interrupt filter. purpose tone detector ports.
Port circuits 3 and 7 provide digital loop-back
Port circuits 2 and 6 are general
testing of each NPE on the circuit pack. The NPE serializes TDM bus signals that are connected to the DSP in serial
form from the NPEs by the DSP interface circuit. Serial clock and data signals connect directly from the NPE to the DSP. The system framing signal is synchronized and connects to the DSP.
The DSP restart circuit controls the DSPs.
When the on-board microprocessor is not functioning properly, the DSP restart circuit takes all of the DSPs out of service. It restarts each individual DSP under control of the port I/O and sanity check circuit.
The touch-tone DSPs, under control of the on-board microprocessor, write data synchronously to the NPEs. The interrupt filter detects valid touch-tone signals and allows end-to-end transmission while blocking end-to-end touch-
tone signaling.
3-54
SYSTEM HARDWARE
TDM BUS LEADS
CIRCUIT PACK
ADDRESS LEADS
BUS
BUFFERS
RED GREEN
LEDS
YELLOW
Figure 3-23.
SAKI
NPE
0
NPE
1
ON-BOARD
MICRO-
PROCESSOR
PORT CIRCUIT 3
PORT CIRCUIT 7
RAM
CIRCUIT
CIRCUIT
Tone Detector (TN748) Circuit
PORT
I/O
SANITY
CHECK
.
PORT CIRCUIT
0
PORT CIRCUIT
1
PORT CIRCUIT
4
PORT CIRCUIT
5
PORT CIRCUIT
2
PORT CIRCUIT
6
TOUCH-TONE PORTS
GENERAL PURPOSE TONE DETECTOR PORTS
3-55
SYSTEM HARDWARE
Pooled Modem (TN758)
The Pooled Modem circuit pack supports 0-300 and 1200 bits per second (bps) data speeds and provides the following:
Circuitry to provide a signal compatible with the modulation formats of
the 212-series modems
Modem emulation (see below)
Capability
0-300 Asynchronous
Data Module Mode
Low 300 Asynchronous 300 Asynchronous 1200 Asynchronous 1200 Asynchronous
Modem control functions corresponding to 212-series modem operations.
A maximum of two Pooled Modem circuit packs are allowed in a single cabinet (six in a 3-cabinet system).
The Pooled Modem circuit pack (Figure 3-24) consists of common circuitry and two conversion resources. The conversion resource (port) allows communications between two dissimilar endpoints. For example, the Pooled Modem circuit pack enables a digital data endpoint linked to an ADU connected to a port on the Data Line circuit pack (TN726) to communicate with either a local analog data endpoint, such as a personal computer with a modem, or a remote host using a central office (CO) trunk connection. Each port has two connections to the TDM bus. One connection is made to the digital data endpoint using an ADU data module. The other connection is made to an analog endpoint.
3-56
SYSTEM HARDWARE
TDM BUS
LEADS
CIRCUIT PACK ADDRESS
LEADS
LEDS
Figure 3-24.
NPE
BUS
BUFFERS
SAKI
RED GREEN YELLOW
Pooled Modem (TN758) Circuit
CONVERSION
RESOURCE
0
RAM
ON-BOARD
MICRO-
PROCESSOR
CONVERSION
RESOURCE
1
3-57
SYSTEM HARDWARE
Common Circuitry: The Pooled Modem common circuitry, which includes all
circuitry shown on Figure 3-24 except the Conversion Resource circuitry, provides the same general function as the intelligent port common circuitry.
Conversion Resources: The two conversion resources (port circuits) are identical and each contains the following:
Microprocessor
Transmit and Receive l-channel Controller (TRIC)
Universal Synchronous/Asynchronous Receiver and Transmitter (USART)
Data USART Clock (DUCK)
Digital Signal Processor (DSP).
The microprocessor controls an on-board data module and modem. This microprocessor communicates with the port circuit microprocessor over a serial control channel. This channel allows the on-board microprocessor to send messages to the port circuit microprocessor specifying call startup information, option settings, information requests, various test modes, and call termination information. It also allows the port circuit microprocessor to inform the on-board microprocessor of various port circuit status information.
The DUCK and TRIC interface l-channel information between the port circuit and the remote data module. The microprocessor controls the operation of the DUCK and the TRIC by programming their internal registers. The DUCK and TRIC together recreate the clock and serial data stream from the remote data module, and process an on-board clock and serial data stream for delivery to the remote data module.
Control information, handshaking, and
RS-232C control leads are passed between the port circuit microprocessor
and the remote data module by the TRIC.
3-58
SYSTEM HARDWARE
The USART interfaces the DUCK’s serial data stream to the conversion
microprocessor. The USART can be programmed by the microprocessor to operate synchronously or asynchronously. The USART also performs the following tasks for the port circuit microprocessor:
Appends start and stop bits to parallel data received from the
microprocessor in the asynchronous mode
Converts serial data received from the DUCK to parallel data
Buffers data in both directions
Detects and generates break characters.
The DSP provides modem emulation. It interfaces the port circuit signal and the remote modem. The microprocessor directs the DSP to execute one of many programs.
The DSP produces data, carrier detection, and timing
information for the port circuit microprocessor.
3-59

SYSTEM SOFTWARE

General

The System software consists of switched services, administrative, and
maintenance software. This software runs on top of the real-time operating system software.

Switched Services Software

The switched services software provides voice and data call processing. This software resides in the Call Processor and Memory circuit packs (collectively referred to as the Common Control circuitry) and in the 8-bit on­board microprocessors located in the port and service circuits.
The switched services software uses the operating system to provide a
process based, message passing, execution environment. The operating system scheduler provides scheduling for the software according to process priority.

Administrative Software

The administrative software provides the control for system rearrangement and change using the System Administration Terminal (SAT). This software resides in the Memory circuit pack and performs the following functions:
Organizes the translation data for administrable entities in the system in
a form that can be viewed and changed at the SAT.
Tests entered data for consistency with data previously entered in order
to avoid such errors as the assignment of the same extension number to two voice terminals. An erroneous or inconsistent data entry is disallowed and an error message is provided.
Causes the translation data to be downloaded, on command, to an
optional Digital Tape Unit (DTU).
4-1
SYSTEM SOFTWARE

Maintenance Software

The maintenance software provides automatic periodic testing of maintenance objects within the system as well as consistency tests among the call status tables within the system. In addition, demand testing is initiated when the system detects a condition requiring a need for testing. Software tables are provided for storing error records. The records can be accessed by maintenance personnel via the SAT. A Permanent System
Alarm (a serious error) causes an alarm indicator on the attendant console to
light and an error record to be stored in the error table.

Memory Allocation

The system software, like the hardware, is identified by release and version number. Each version identifies a particular memory configuration for the release number. Main memory is located in the Common Control circuitry.
The operating system and error log software resides on the Call Processor
circuit pack, and the remaining administration and call processing software is
on the Memory circuit pack.
4-2
SYSTEM SOFTWARE

Real-Time Constraints

Real-time constraints are a function of the speed of the Common Control circuitry and the traffic load. The switch is designed so that many time­consuming and repetitious functions are performed by processors in the port and service circuit packs, thus relieving the common control circuits.
Traffic load, defined as the sum of static and dynamic loads, is a function of the number of features that are executed, the frequency with which they are executed, the system configuration,
and the instantaneous (peak) call processing load. The configuration contribution to load is known as dynamic load. The static load consists of maintenance and audit routines.

Software Partitioning

System 25 software is comprised of various modules, each supporting a
particular process. following:
Administration
Station Call Processing
SMDR Call Record Processing
Trunk Call Processing
Typical modules (referred to as tasks) include the
Dial Plan Manager
Event Timer
Save/Restore (Administration function)
Maintenance and Audit Functions.
As shown on Figure 4-1, software tasks associated with the Memory circuit pack are Administration and Feature Code Modules. The Feature Code Modules includes Station Call Processing.
Each task controls the storage and movement of data and messages between associated elements within the system.
4-3
SYSTEM SOFTWARE

Memory Circuit Pack

Administration: Provides for administration of station and system features.
This software also supports maintenance procedures related to checking errors and diagnosing trouble.
Feature Code Modules: Includes the software that sends and receives data to/from the Operating System as well as controls all voice and data features supported by the system.
Station Call Processing includes the processing of messages and data associated with voice terminal on-hook/off-hook indications, associated port identifications, and button and light-emitting diode
(LED) operations.
The Station Message Detail Recording (SMDR) software generates SMDR records associated with a particular call. The records are then sent to the System RAM for storage and then to the SMDR output channel.

Call Processor Circuit Pack

System RAM: Provides for the storage of the following:
Variables for the various software tasks
System translations
Error Records
Feature Code Data
Stack.
Error Logger:
Prioritizes and stores system errors. The errors stored in the
three error records (located in System RAM) are:
Permanent System Alarms
Transient System Errors
Most Recent System Errors.
The Error Logger lights the Alarm LED (located on the Attendant Console) when a serious error is detected.
4-4
SYSTEM SOFTWARE
Operating System (OS): Controls all message and data flow to/from the
Memory circuit pack and the Arch Angel Driver Interface to the microprocessors on the port circuit packs, and to RS-232C driver interfaces. Messages destined for a particular task are queued until the associated task
can receive them. When a task has completed a particular process, the next
message is obtained from the task’s message queue. The OS provides an interval timer that is used to time tasks. Processes that exceed the set
interval (approximately 60 seconds) are terminated by the OS.
Arch Angel Driver Interface:
Network Control (NC).
RS-232C Driver Interface: Handles the flow of information between the Call
Processor circuit pack and the system’s peripheral equipment (that is, System Administration Terminal, Digital Tape Unit, SMDR Output Device).
Provides an interface between the OS and

TDM Bus

Provides an electronic link among the system port circuits (including System Resources) and between the Call Processor circuit pack and port circuits.

Port Circuit Packs

Each port circuit pack has on-board software that provides for the sending/receiving of Network Control messages and data. Circuit pack status messages are also sent to the Network Control software.
4-5
SYSTEM SOFTWARE
MEMORY CIRCUIT PACK
ADMINISTRATION
(TASK)
FEATURE CODE MODULES
STATION
CALL
PROCESSING
(TASK)
SMDR
PROCESSING
(TASK)
CALL PROCESSOR CIRCUIT PACK
TDM BUS
PORT CIRCUIT PACKS
SYSTEM
I/O
SYSTEM RAM
MESSAGE
SEND/RECEIVE
OPERATING SYSTEM
ARCH ANGEL
DRIVER
INTERFACE
NETWORK CONTROL
SOFTWARE
CONTROL
CHANNEL
MESSAGES
ON-BOARD SOFTWARE
PORT STIMULI
VOICE TERMINALS,
CO FACILITIES, DTU, SMDR
RS-232C DEVICES
RS-232C
DRIVER
INTERFACE
SAT,
ERROR
LOGGER
Figure 4-1.
4-6
System Software Partitioning
SYSTEM SOFTWARE

Step-By-Step Call Description

The following is a description of a call originated between two multiline voice terminals.
1.
A microprocessor on a station port circuit pack (port controller) continually status/change and button presses.
When a user goes off-hook, the port controller detects the change.
2. The port controller sends an off-hook up-link message along with port
3. identification to the Call Processor Network Controller (CPNC) via the TDM bus.
The CPNC accepts the message and forwards it to the Operating
4. System (OS) via the Arch Angel Driver Interface.
The OS checks a message directory to determine which task (that is,
5. software module) is to receive the message. A function of the OS, referred to as the “transformer,” determines it has a message for the
Station Call Processing task and queues the message in Random Access Memory (RAM).
The Station Call Processing task retrieves its message and interprets
6.
it as a call origination. The task determines whether there is an idle call appearance button (System Access button) on the called voice terminal. connection.
monitors associated port circuits for switchhook
If so, two available time slots are reserved for the
The task sends downlink messages to the port circuit via the OS. The
7. messages instruct the port circuit to listen for dial tone on a specified
time slot and to light the call appearance status LED on the terminal. When the user dials the first digit, the port circuit determines the digit
8.
dialed. It then listens to appropriate time slots on the TDM bus for the two tones used to generate an equivalent Dual-Tone
Multifrequency (DTMF) signal.
the DTMF signal back to the user until the user releases the button. The port circuit sends an up-link message with each digit dialed to the
9.
OS which routes them to the Dial Plan Manager (DPM). The DPM collects the dialed digits and determines that the call is a
10.
station-to-station call.
It then removes dial tone and feeds
4-7
SYSTEM SOFTWARE
11.
When the DPM collects enough digits to identify an extension number, it stops collecting digits.
Note: If the extension number dialed is invalid, the DPM sends a
down-link message to the port circuit instructing it to listen to time slot 07 (Reorder Tone) that is then heard by the user. Go to Step 18.
12.
A down-link message is sent to the originating port instructing it to listen to time slot 06 (busy) or 08 (ringing), as appropriate. Go to Step 18 for Busy Tone or an unanswered call.
13.
Station Call Processing sends a down-link message to the station port circuit pack associated with the called extension to turn on the terminal’s ringer and to flash the call appearance LED.
14.
When the called party lifts the receiver, the associated port circuit pack controller sends an off-hook message to the OS as before.
The Station Call Processing task, when it receives the message,
15. interprets the off-hook message as an answer.
The task sends a down-link message to the called port circuit to turn
16.
off the ringer and to change the flashing LED to steadily lighted.
4-8
17.
Down-link messages are sent to the port circuits assigning talk and listen time slots for the connection.
18.
When either of the parties hangs up, the associated port circuit controller sends an up-link message to the Station Call Processing task.
19.
Station Call Processing interprets the on-hook message as the end of the call.
The task then sends a down-link message to the port circuit pack
20. controllers to disconnect the time slot connections and turn off the LEDs associated with the calls.

MAINTENANCE STRATEGY

Fault isolation is the cornerstone of the System 25 maintenance strategy. Maintenance activity isolates faults to one (or more) repairable or replaceable
maintenance units. Equipment should be tested in the following order:
1.
Terminal equipment
2.
Station wiring
3.
Port circuit packs (CPs)
4.
Common control circuitry Power supply and cabinet
5.
6.
Backplane.
The first fault isolation step attempts to reproduce the fault, whether it is
system-detected or user-reported.
diagnosed more easily and its correction confirmed.
Figure 5-1 presents a practical approach in responding to system troubles. If the maintenance technician is sent to a System 25 site in response to a trouble report, the maintenance activity will probably consist of isolating and replacing one or more faulty units of equipment. Multiple faults recorded in the error log and user-reported troubles may require more investigation and analysis.
If a fault can be reproduced, it can be
5-1
MAINTENANCE STRATEGY
SYSTEM TROUBLE
REPORTED
CAP ALARM REPORTED
READ PERMANENT
SYSTEM ALARMS
TABLE IN ERROR
LOG;
AND CHECK
CIRCUIT BOARDS
AND POWER LED
STATUS
TYPE OF TROUBLE INDICATED BY THE LEDS AND ERROR LOG
PORTS POWER CPU/MEMORY
SUPPLY CABINET FRONTPLANE/ OR FANS
ISOLATE TROUBLE TO RUN
REPLACEABLE MAINTENANCE
UNIT (SEE TEXT)
USER-REPORTED
CAP ALARMED
SYSTEM DOWN OR CANNOT
ACCESS ERROR LOG
CHECK POWER SUPPLY LED AND FANS
CPU/MEMORY SERVICES CIRCUIT FRONTPLANE/ BACKPLANE DIAGNOSTIC
SERVICE CIRCUIT BACKPLANE
DIAGNOSTIC
l
DISCUSS THE TROUBLE
WITH SYSTEM USERS
READ (1) PERMANENT SYSTEM DEFECTIVE POWER SUPPLY
REPLACE
POWER SUPPLY
RECREATE USER-REPORTED TROUBLE
STATIONS TRUNKS
STATION TRUNK TEST(S)
SEQUENCE
ALARMS, (2) TRANSIENT
SYSTEM ERRORS TABLE, AND/OR (3) MOST RECENT SYSTEM ERRORS IN TABLE
ERROR LOG;
AND CHECK CIRCUIT
BOARDS AND POWER SUPPLY
LED STATUS
ERROR LOG CONFIRMS
USER-REPORTED TROUBLE
NO ERROR LOG RESULTS
RUN
TEST(S)
SEQUENCE FIRST, WARM
(DEPENDING
ON PROBLEM
SEVERITY)
START. IF
PROBLEM PERSISTS
RESTORE
TRANSLATIONS
FROM TAPE. IF
PROBLEM PERSISTS
ESCALATE.
OTHER
Figure 5-1.
5-2
Response to System 25 Trouble Report
MAINTENANCE STRATEGY

General Procedures

Sometimes, faults recorded in the error log and user-reported troubles will exist at the same time. The logged faults should always be cleared first, if possible. This procedure often clears the user-reported troubles without any additional maintenance.
Clearing the most serious logged fault may clear some or all of the other faults. Descriptions of the errors in the error log indicate their relative urgency.
Error log records should be manually recorded before clearing a recorded error or alarm. If a faulty CP is located in the process of clearing a problem, it must be replaced with a known good CP. The associated error record should be included with the CP when it is returned for repair. If the System Administration Terminal (SAT) has an associated printer, the error records
can be printed instead of being manually recorded. Traditional trouble-shooting methods still have a valid place in maintaining a
system as advanced as System 25. Indeed, they are sometimes sufficient to locate and clear faults. These methods include voice terminal substitution, visual inspections, continuity checks, and clarification of operating procedures with users.

Total System Failures

As the flow chart in Figure 5-1 shows, a failure of the common control circuitry (that is, Call Processor,
repaired immediately. This may clear other problems in the system as well.
Memory, and Service Circuit) must be

Port Problems

Port CP failures can usually be cleared by replacing the CP displaying the lighted red light-emitting diode (LED) (if reseating was unsuccessful). When replacing suspected defective CPs, it is desirable to wait until the amber LED (indicating CP is in use) turns off before removing the pack. (See “Interpreting Circuit Pack LEDs” in Section 8, for additional information on CP LEDs.)
5-3
MAINTENANCE STRATEGY

Common Control Problems

Common Control circuitry is difficult to troubleshoot and replace. The system must be powered down before any of these CPs are replaced. Before powering down, translations should be saved to tape (see Section 7
“Operating the Digital Tape Unit”). Other repair procedures may also require the system to be powered down. the following
Visually inspect the CP. If a problem is identified, attach a note to the CP identifying the problem.
Attach any error reports that may apply.
Visually inspect cabinet backplane.
After the suspected faulty pack has been replaced, the system can be
powered up. Replacing the Call Processor CP causes all historical alarm data
to be lost. The system will then have to be restored from the tape backup
unit with the latest copy of the system’s translations. If no tape exists, the
system has to be reinitialized. Also increasing the common control trouble-clearing difficulty is the high
degree of interaction between the CPs. are more likely to occur in common control problems than in port problems.
Use of the error log is imperative in clearing common control problems.
After removing a suspected faulty CP, do
Multiple errors and off-board errors

Station, Wiring, and Trunk Problems

If the system indicates that a fault is with station, or if a user complaint indicates a station problem, the trouble must be isolated to the station itself or to the wiring between the cabinet or station interconnect panel and the station.
A visual inspection of station wiring, particularly the mounting cord, is suggested in cases of station trouble reports. A dead station can result from the mounting cord being pulled loose.
wiring is crushed or severed by furniture or traffic. Stations can be swapped with known good stations of the same type to help isolate the trouble.
Trunk problems reported by alarms or by users can be evaluated with tests from stations or by interpreting the error log. if trunk troubles appear to be outside the System 25, the responsible common carrier should be asked to make repairs.
5-4
Station trouble can also occur when
MAINTENANCE STRATEGY

Automatic Maintenance Tests

Because System 25 maintenance tests are performed automatically, there is no provision for users or technicians to initiate maintenance tests. The error log is read by entering commands from the SAT. Additional information that may be of help in clearing complex or subtle troubles is also available via the SAT (for example, the record of port locations).
Refer to Administration Manual (555-520-500) for your system for information
on using “Search” procedures from the SAT as an aid in troubleshooting.

Maintenance Failure

If a System 25 equipment problem cannot be corrected using the procedures in this manual, the technician should follow established maintenance escalation procedures.
5-5

ERROR LOG

The error log is accessible via the System Administration
using the following procedures. The Error Log is comprised
Terminal (SAT)
of the following
three error tables:
Permanent System Alarms
Transient System Errors
Most Recent System Errors.
Each error record is reported as one line on the SAT (80 characters or fewer). Permanent System Alarms and Transient System Errors tables use the same format. These error records provide the location of the error [by port and circuit pack (CP) type], the date and time of the first occurrence and last occurrence of the error, the number of times the error has occurred, and a description of the error.
A typical error record from the Permanent System Alarms and Transient
System Errors table is as follows:
PORT
BOARD FIRST
NUMBER CODE
10201
ZTN82 23/12:30
PERMANENT
OCCURRED
SYSTEM ALARMS
LAST COUNT
OCCURRED
30/01:56
6
NAME
System Restart
Interpret this record as follows:
“Port Number” 10201 is the 5-digit port identification number specifying
the location of the error. The first digit indicates the cabinet (1-3), the
next two digits indicate the slot within the cabinet (01-12), and the last
two digits indicate the port number on the CP in the slot (01-16).
“Board Code” ZTN82 is the CP on which the error occurred (or that is
associated with the error if this is an off-board error).
“First Occurred” 23/12:30 is the date and time of the first occurrence of
this error. The date is assumed to be the current year and month. A 24-hour clock is used.
6-1
ERROR LOG
“Last Occurred” 30/01:56 is the date and time of the last occurrence of this error. The date is assumed to be the current year and month. A 24-hour clock is used.
“Count’’ 6 is the number of times this particular error has occurred.
“Name” System Restart is a description of the nature of the error.
Descriptions are self-explanatory.
Error records in the Most Recent System Errors table have a slightly different
format. Atypical error record from the Most Recent System Errors table is
as follows:
MOST RECENT SYSTEM ERRORS
PORT BOARD DATE
TIME
NAME
NUMBER CODE OCCURRED OCCURRED
10201
ZTN82 03/12/85
12:01:56
ArchAngel Insane Restart
Interpret this record as follows:
“Port Number” 10201 is the 5-digit port identification number.
“Board Code” ZTN82 is the CP on which the error occurred (or that is
associated with the error if this is an off-board error).
“Date Occurred” 03/12/85 is the date this error occurred. A
conventional calendar designation is used.
“Time occurred” 12:01:56 is the time this error occurred. A 24-hour clock is used.
A combined total of 40* (V1) or 50* (V2) error records for Permanent System Alarms and Transient System Errors is stored by the system. Ten error records are stored in the Most Recent System Errors table. Errors are displayed in chronological order.
*
Two or more instances of the same error result in only two entries in the log (that is, the first and last occurrence).
6-2
ERROR LOG
The error log is under the control of internal background maintenance software that automatically escalates an error to a more serious category or retires it. The system tests itself after a repair has been made. If the error condition is corrected, the error may be removed from the error log.
Although some errors are automatically retired from the error log, they can also be manually retired by entering commands at the SAT. Alarms, conditions that light the alarm light-emitting diode (LED) on the attendant console, can also be manually retired in the same way.

Accessing the Error Log From the SAT

Follow these steps to read any of the tables in the error log from the SAT:
1.
Confirm that the SAT is properly connected to the Call Processor CP administration port.
If the SAT has a selectable baud rate, set it to 1200 baud.
2. Be sure transmission parity is set to none, with the parity bit set to
3. space (0).
Note: For the AT&T Model 703 SAT, four pencil switches under
the paper compartment cover are set as follows: switches 1
and 3 to “Off;” switches 2 and 4 to “On.”
4.
Turn on the terminal and press the carriage return character once or twice. On most terminals, this key is <RETURN> or <ENTER>.
After communication with the system is established, a prompt is
5. displayed:
Enter Password ->
6.
Obtain the password from the system administrator. Enter the
password and press <RETURN>.
the prompt: Make one selection from menu ->.
7.
Enter 8 (for the SEARCH selection) and press <RETURN>.
The main menu is displayed with
6-3
ERROR LOG
The SAT displays:
8. When search is defined type c to search >Action=
Enter 1 and <RETURN>.
9.
10. The SAT displays:
SEARCHES: ACTION=1 DATA=
11. Enter D. The system completes the word Data followed by the =
sign.
12. After Data= enter one of the following numbers, depending on which
error table you wish to see:
30 to see Permanent System Alarms
31 to see Transient System Errors
32 to see Most Recent System Errors.
If you select 30, for example, the system responds with: SEARCHES: Action=1 Data= 30.
Now, enter the letter c to begin the search of this table. The c must be
entered repeatedly to access each line. To remove a record from the Permanent System Alarms or Transient System
Errors table, enter the letter r.
If you enter a letter incorrectly, press the backspace key. Each time you press this key, one character is erased.
When you finish viewing one of the error log tables and want to view another error log table, enter D.
The system completes the word Data followed by the = sign. Now enter the appropriate number for the table you want to view. (See preceding Steps 11 and 12.)
If you want to return to the main menu at any point, type M and <RETURN>, To sign off, simply turn off the terminal.
6-4
ERROR LOG

Error Log Dictionary

The following provides a listing of error messages displayed on the SAT and an associated description of each.
AC Power Failure: An indication that ac power has been lost (for example,
plug removed from a wall receptacle, building power down, etc.)
Alarm Log Overflow:
written to them. This error is kept, however, to alert you of the fact. Arch Angel Insane Restart: Clocks may be missing from the TDM bus. Make
sure TDM bus terminators are plugged in. is plugged in and that the cables connecting the cabinets are okay. Check Call Processor CP.
Arch Angel Interrupt Restart: System restarted due to Call Processor
problem. Check Call Processor CP if the error occurs frequently. Problem could be software related.
Bad Data: (Other than CPU or Memory) Data portion on a down-link
message invalid. System may recover from this error.
Bad Major Heading: (Other than CPU or Memory) Header portion of a down-link message is invalid. System may recover from this error.
Bad Oat Device: (STARLAN Interface CP) This error is an isolated transient condition that is normally recoverable.
Bad Port: (STARLAN Interface CP) This error is an isolated transient condition that is normally recoverable.
Bad Port Number: Port number on a down-link message is invalid. System
may recover from this error.
The error logs are full and no more errors can be
Insure that the Service Circuit CP
6-5
ERROR LOG
Bad Port Translations: Service Circuit or Tone Detector. Receiver requested to listen to time slots that do not have tones on them. System may recover from this error.
Bad Ringing Supply:
Problems detected with ringing portion of power
supply.
Bad Sub Qualifier: (Other than CPU or Memory) Invalid message type on a down-link message. System may recover from this.
Belated External Release: See “No External Release On PBX Disconnect.”
Board Initialization Audit Error: (Other than CPU or Memory) System may
recover from this.
Buffer Deallocation Failure: (STARLAN Interface CP) This error resets the
CP. If the reset is successful, then the error is transient and recoverable. If
the reset fails, the CP should be checked.
Bus Error Test Failed: Bus error circuitry failure. Replace CPU. Cold Start: System was restarted for some reason (CP unplugged, power
problem, or some other error).
Translations may be corrupted if the Call
Processor or Memory CP is removed while in use or if power supply shuts
down for any reason other than ac power failure (+5 V shorted, overheat). The system initializes itself to the default state. A translation restoration is
required to reinstate customer specific data.
CPU ROM Checksum Error: CPU has failed the ROM test. Check Call
Processor CP.
DC Fail Check: Indicates the absence of +5 V dc on a cabinet. Each cabinet has its own power supply; therefore, this may not cause a Warm Start.
DC Fail Transient Record: This message is provided when dc power fails. It
provides a record of the length of the outage.
6-6
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