ATT System 25 Maintenance Manual

GENERAL MAINTENANCE INFORMATION
lCall 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.
lPower 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...

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:
lDigital Switch
l
l
l
l
l
l
l
l
lStation 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 HARDWARE
DIGITAL SWITCH
STARLAN
CP (V2)
AUX TRUNK CP
DATA LINE CP
STATION CP
CALL
PROCESSOR
CO
TRUNK CP
STATION CP
CO
TRUNK CP
STATION CP
(OPS)
TIE
TRUNK CPNETWORK EXPANSION UNIT
66–TYPE
BLOCK
AUXILIARY EQUIPMENT
SIP
RS–232C TERMINALS
VOICE TERMINALS, ADJUNCTS,
AUXILIARY EQUIPMENT
P/O SIP
SAT
DTU
SMDR/CAS
10B ETU
-48V
-48VSIP
CPUP/O
SIPPOWER FAILURE
TERMINALS
700A (110-TYPE) OR
157BF (66-TYPE) BLOCKS
NETWORK ACCESS TRK
LINE
CO
P/O
SIPRJ21X
RJ21X
RJ21X
RJ21XCO
LEGEND :CAS -
CO -
DTU -
ETU -
OPS...

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...

SYSTEM HARDWARE
DIGITAL SWITCH
STATIONC2— — —(1)
CIRCUIT— — —
PACK— — —(8)
PART OF SIP
UNTERMINATED
4-PAIR
BUILDING
WIRE
858A
ADAPT.
858A
ADAPT.
MODULAR
JACKS
VOICE TERMINALS,
ADJUNCTS,
POWER UNITS
LEGEND:C2 – OCTOPUS CABLE (WP90780) - PEC 2720-05P858A ADAPTER (FURNISHED BY INSTALLER) -
SIX 4-PAIR MODULAR JACKS TO
SIX 11O-TYPE CUTDOWN BLOCKS
Figure 3-2. Typical Station Interconnect Panel (SIP) Connections
3-4 

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. The 700A [110-type or 66-type (157BF)]
Connector Blocks are connected to RJ21X or RJ2GX network interfaces by
25-pair single-ended cables. Incoming central office trunks are sorted on the
700A blocks into sets of up to eight trunks of the same type. These blocks
are then connected to the...

SYSTEM HARDWARE
LEGEND:A-
B-
C-
OPS -
SIP -
D-
E-
*-SINGLE-ENDED 25-PAIR CONNECTOR CABLE (A25D)*
3 TO 1 SPLITTER CONNECTORIZED CABLE (OR6016) - PEC 2720-06X
2 TO 1 SPLITTER CONNECTORIZED CABLE (OR6015) - PEC 2720-05X
OFF-PREMISES STATION
STATION INTERCONNECT PANEL*
OCTOPUS CABLE (WP90780) - PEC 2720-05PINSIDE WIRE*
FURNISHED BY INSTALLER
Figure 3-3. Trunk Access Equipment Connections
3-6 

SYSTEM HARDWARE
Terminal Equipment
System 25 terminal equipment includes various voice terminals,
Asynchronous Data Units (ADUs), data terminals, attendant consoles, and
auxiliary equipment. System 25 supports three types of voice terminals:
7300H series, Single-Line [Tip & Ring (touch-tone or rotary*)], and MET
(Multibutton Electronic Telephone). Each type of voice terminal must be
connected to a compatible port CP.
ADUs provide the interface between the system and data equipment
connected to the Data...

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:
l Common Control
— Memory Bus
— Call Processor CP
— Memory...