AT&T System 25 R1V1_R1V2 Maintenance Manual

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555-520-105 Issue 2, October 1987

AT&T SYSTEM

MAINTENANCE

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

TRUNK CP

STATION CP

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

- SYSTEM ADMINISTRATION TERMINAL

- STATION INTERCONNECT PANEL

- STATION MESSAGE DETAIL RECORDING

P/O SIP

NETWORK ACCESS

POWER FAILURE TERMINALS

RJ21X RJ21X

RJ21X

RJ2GX

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

(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)

ANALOG

LINE CP

(TN742)

700A NETWORK

INTERFACE BLOCKS

(110-TYPE OR

66-TYPE)

__________ I I

I I

I A I

CO NETWORK INTERFACE

FACILITIES

(LOOP AND GRD. START TRUNKS,

OPS, DID TRUNKS)

RJ21X

———————

CENTRAL

OFFICE

TIE TRUNK FACILITIES PORT CP(S)

LEGEND:

Figure 3-3.

3-6

I I 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 A I

I I

RJ2GX

TIE LINE

—————

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

EIA CHANNELS

( RS-232C )

SERIAL SERIAL

CHANNEL CHANNEL

SYSTEM HARDWARE

TO EMERGENCY

TRANSFER UNIT

(ETU)

SERIAL

CHANNEL

-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

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

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

4 5

256 TIME SLOTS

_______

255 0

TDM Bus Time Slot Generation (Not a Timing Diagram)

3-17

SYSTEM HARDWARE

Table 3-A.

TIME SLOT NO.

thru

06 07 08 09 10 11 12 13 14

17 18 19

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

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

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

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)

MODEM

(212-TYPE)

_ _ _ _ _ _ _ _ _ _ _ _

SAT, SMDR,

CAS (OFF-PREMISES

SWITCHED CONNECTION)†

MODEM

(212-TYPE)

†OFF-PREMISES STATION

OR CO TRUNK

OPS

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

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

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

HYBRID

T.O

R.O

ON-BOARD MICROPROCESSOR

Figure 3-11.

3-30

PORT

I/O

CIRCUIT

GROUND

DETECTOR

CIRCUIT

PORT

CIRCUIT

PORT

CIRCUIT

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

HYBRID

T.O

R.O

ON-BOARD MICROPROCESSOR

Figure 3-12.

3-32

PORT

I/O

CIRCUIT

PORT

CIRCUIT

PORT

CIRCUIT

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

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

PORT

CIRCUIT

PORT

CIRCUIT

ELECTRONIC

BATTERY

FEED

T.O

R.O

T.3

R.3

T.4

R.4

T.7

R.7

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

NPE 1

PROTOCOL

HANDLER

PORT CIRCUIT PORT O

ANALOG PORT

CODEC

HYBRID

TRANSCEIVER

ELECTRONIC POWER FEED

CIRCUIT

PORT

CIRCUIT

DATA

PORT

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

ON-BOARD

MICROPROCESSOR

NPE

BUS ISOLATION

BIT

CLOCK

PORT CIRCUIT O

PROTOCOL

HANDLER

(OATMEAL)

ASYNCHRONOUS

DATA UNIT (ADU)

PORT

CIRCUIT

PORT

CIRCUIT

PORT

CIRCUIT

PORT

CIRCUIT

PORT

CIRCUIT

PORT

CIRCUIT

PORT

CIRCUIT

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

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

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

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

INTERFACE

TRUNK

UNIT

HYBRID

T.O

R.0

ON-BOARD MICRO-

PROCESSOR

Figure 3-18.

PORT

CIRCUIT

PORT

I/O

CIRCUIT

PORT

CIRCUIT

PORT

CIRCUIT

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

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

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

S85

DIMENSION PBX

Other

Preferred

Signaling Format

System 25

Simplex Type 5

E&M Type 1 Compatible

Prot. Type 1 Compatible

E&M Type 1 Compatible

Far-End

Simplex Type 5

E&M Type 1 Standard

Prot. Type 1 Standard

E&M Type 1 Standard

Set

E&M/

SMPLX

Option Switch

SMPLX

E&M

Unprot Option Switch

Either

Unprot

Prot

Unprot

Set

Prot/

Administer

the Port

Type 5

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

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:

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

PORT

I/O

CIRCUIT

Figure 3-21.

3-50

GROUND

DETECTOR

PORT

CIRCUIT

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

ON-BOARD

MICRO-

PROCESSOR

PORT CIRCUIT 3

PORT CIRCUIT 7

RAM

CIRCUIT

Tone Detector (TN748) Circuit

PORT

I/O

SANITY

CHECK

PORT CIRCUIT

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

RAM

ON-BOARD

MICRO-

PROCESSOR

CONVERSION

RESOURCE

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.

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

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

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

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:

Terminal equipment

Station wiring

Port circuit packs (CPs)

Common control circuitry Power supply and cabinet

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

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

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:

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.”

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 ->

Obtain the password from the system administrator. Enter the

password and press <RETURN>.

the prompt: Make one selection from menu ->.

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>.

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

AT&T System 25 R1V1_R1V2 Maintenance Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

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

Digital Tape Unit

Common Control and Switching Network

Common Control

Switching Network

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

ERROR LOG

Accessing the Error Log From the SAT

Error Log Dictionary