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 (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.
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							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.
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							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 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.
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							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 -CALL ACCOUNTING SYSTEMP/O - PART OF
CENTRAL OFFICESAT- SYSTEM ADMINISTRATION TERMINAL
DIGITAL TAPE UNITSIP- STATION INTERCONNECT PANEL
EMERGENCY TRANSFER UNITSMDR- STATION MESSAGE DETAIL RECORDING
OFF-PREMISES STATION
Figure 3-1. System 25 Block Diagram
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							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 cabinets 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:
l
lZ210A—Six 4-pair modular jacks to six 4-pair modular jacks
858A—Six 4-pair modular jacks to six 110-type cutdown blocks.
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							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
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							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 cabinets with splitter cables.
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							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
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							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 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.
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.
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							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 CP
l Switching Network
— TDM (Time Division Multiplex) Bus
— Port Circuits
— System Resources
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