ATT System 25 Installation And Maintenance Manual

							NOTES :
1.
2.
3.
4.
5.115V AC, 60 Hz, 15 AMP OUTLETS
(HUBBELL 5262 OR EQUIVALENT)
MUST BE LOCATED WITHIN 4 FEET
OF SYSTEM CABINETS.
MULTIPLE CABINET SYSTEMS REQUIRE
TWO QUAD OUTLETS, SINGLE CABINET
SYSTEMS REQUIRE ONE QUAD OUTLET.
ALLOW AT LEAST 24 INCHES OF SPACE
IN FRONT OF CABINETS. TABLE MUST
BE ABLE TO SUPPORT 250 POUNDS.
BACKBOARD IS 3/4 INCHES THICK BY
48 INCHES WIDE BY 96 INCHES LONG
(FOR MAXIMUM SYSTEM).
SYSTEM 25 CABINETS AND BACKBOARD
MUST BE LOCATED IN A RESTRICTED
ACCESS AREA.
RESTRICTED
ACCESS AREA
(NOTE 5)
Figure 2-8.Typical System 25 Floor Plan
2-17 
						

							INSTALLATION
AC Power
All cabinets and any locally-connected System 25 peripheral equipment
(System Administration Terminal [SAT], Station Message Detail Recording
[SMDR] device, Digital Tape Unit [DTU]), and Customer Service Unit (CSU)
used for DS1 connections must be plugged into the common ac power outlet.
This outlet must have an associated ground block connected to an approved
building ground, using #6 AWG copper wire. (This ground block is the
system’s single-point ground.)
A 1-cabinet system requires one quad ac outlet. A 2- or 3-cabinet system
requires a second quad outlet and two separately fused 15-ampere circuits.
Additional ac outlets may be needed for auxiliary equipment. All ac outlets
must have the safety ground (green wire) cross-connected to the single-point
ground block on the first quad outlet. (See Figure 2-9.)
Local options may require that surge protectors be used for all peripheral
equipment used with the System 25, including the Customer Service Unit
(CSU).
Grounding
For proper grounding instructions, refer to the AT&T System 25 Electrical
Protection and Exposure Check List (555-500-1 20).
Warning:Verify that the building ground has been provided by
one of the methods listed below, that ac power uses
approved building ground for its primary ground, and
that all voltage limiting devices are grounded to building
approved ground.Improper ground can result in
equipment failures and service outages from lightning
induced surges on the power lines.
An approved building ground for System 25 may be one of the following,
listed in decreasing order of preference:
1.Building steel.
2. Acceptable water pipe—
a metal underground water pipe at least 1/2
inch in diameter, in direct contact with the earth for at least 10 feet.
The pipemust be electrically continuous (or made electrically
continuous by bonding around insulated joints, plastic pipe, or plastic
water meters) to the point where the protector ground is connected.
A metallic underground water pipe must be supplemented by the
2-18 
						

							INSTALLATION
3.
4.
metal frame of the building, a concrete encased ground, or a ground
ring. If these grounds are not available, the water pipe ground can
be supplemented by one of the following types of grounds.
l Metal underground gas piping system—an electrically
continuous metal underground gas piping system that is
uninterrupted with insulating sections or joints and without
an outer nonconductive coating.
l Other local metal underground systems or structures—local
underground structures such as tanks and piping systems.
l Rod and pipe electrodes—
a 5/8-inch (solid rod) or 3/4-inch
(conduit or pipe) electrode driven to a minimum depth of 8
feet.
lPlate electrode—expose a minimum of 2 square feet of
metallic surface to the exterior soil.
Concrete encased ground—defined to be an electrode, consisting of
at least 20 feet of one or more steel reinforcing rods at least 1/2 inch
in diameter, or 20 feet of bare copper conductor not smaller than #4
AWG encased in 2 inches of concrete. This electrode must be
located within and near the bottom of a concrete foundation or
footing that is in direct contact with the earth.
Ground ring consisting of at least 20 feet of bare copper conductor
not smaller than
must be in direct
below the earth’s
Lightning Protection
#2 AWG encircling the building. The ground ring
contact with the earth and buried at least 2.5 feet
surface.
System 25’s lightning protection plan involves five distinct but interdependent
items required at every installation:
lPrimary protection in the form of voltage limiters (typically carbon
blocks or gas tubes) on all pairs that leave the building, whether
aerial or buried. These devices bypass surges to approved building
ground and limit potential differences between T/R pairs and building
ground to less than 1500 volts.
2-19 
						

							INSTALLATION
l A single-point ground (SPG) system in which the green wire ground
(system ground) and the telephone company ground are connected
to approved building ground.
l The coupled bonding conductor must be connected between the
telephone company ground at the building entrance and System 25’s
SPG.
l Surge protection on the ac power to System 25.
For greater than 99 percent of all lightning strikes, the protection outlined
above will do the job.However, there are a few locations where the
described protection may not be sufficient.
External secondary protection,
located at the trunk access area of the System 25 cross-connect field, can be
employed.
Several commercial units are available.If 66-type block terminations are
used, a very convenient device is the LP5-230-220 Fused Lightning Protector.
This unit plugs into the 66-block (in place of the shorting bars) and includes
the sneak current fuse. One unit is required per protected pair. A ground
bar is provided with the lightning protection units or can be ordered
separately (Comcode 901-007-120). All lightning protectors located in the
System 25 cross-connect area must be grounded to System 25’s SPG via a
#6AWG copper wire.
In addition, an AC Surge Suppressor (Tll Model 428) may be required. Local
practice should be followed.The unit plugs directly into one of the quad
outlets and provides a dual outlet to protected equipment. Sufficient units
should be provided to protect all at-powered equipment. Each cabinet in the
system requires a protected outlet, and in addition, a protected outlet is
required for each auxiliary unit, such as the SAT, a tape unit, or a printer.
When a Surge Suppressor is used,all peripheral equipment directly
connected to System 25 must be connected to alternating current via the
Surge Suppressor.
2-20 
						

							INSTALLATION
Secondary Protection
External secondary protection,located at the trunk access area of the
System 25 cross-connect field, is required for all trunks and off-premises
lines. Refer to Table 2-B for approved trunk protectors.
FROM AC
LOAD CENTER
(TWO SEPARATELY
FUSED 15 AMP
CIRCUITS)
SINGLE
POINT
GROUND
HGROUNDI
LOAD
CENTER
II
(GREEN)
(#14 AWG)
I
/TO CABINET NO. 1
GROUND BAR MOUNTED ‘GROUND BLOCK (MAX.
ON 4“ BOX (SQUARE DLENGTH =20 FT.)
PK9GTA OR APPROVED
EQUIVALENT)4“ BOX (RACO 230
OR EQUIVALENT)
HUBBELL RECPTS.
( 5262 15 AMP
OR EQUIVALENT)
4“ COVER (RACO 807
OR EQUIVALENT)
APPROVED
BUILDING GROUND
(#6 AWG, COPPER)
Figure 2-9.AC Power Distribution—Multiple Cabinet System
2-21 
						

							INSTALLATION
Building Wiring
Building (station) wiring (must be 24 AWG or heavier) from voice and data
terminals to the equipment location should already be in place. System 25
wiring requires that 4-pair circuits be distributed from the equipment location
to each station’s wall jack.The SIP hardware (Figures 2-2 through 2-6),
designed specifically for this purpose, is furnished with each system. Except
in extraordinary circumstances, this cross-connect hardware must be used.
In unusual circumstances where the 617A Panels are not used and some
other cross-connect equipment that does not provide a modular jack interface
to the port circuits is used, separate 4-pair circuits must be run for the voice
and data terminal at the workstation.
All examples and instructions in this
The station wiring terminations inmanual assume
the equipmentthat a SIP is used.
area should have been
labeled to indicate the room location and jack number of the other end of the
line. When SIP connections are made, the connection information should be
entered on the Voice and Data Station Records Form (see Install Equipment
Room Station Cabling in this part for details).
2-22 
						

							INSTALLATION
INSTALL SYSTEM CABINETS
Before beginning the cabinet installation, position the cabinet table within 2
feet of the ac power receptacle. Make sure that the cabinets are easily
accessible from both the front and the back.
Position Cabinet(s)
Caution:A fully-equipped cabinet weighs 80 pounds.
1.
2.
3.
4.
Check
Unscrew and remove the upper rear panel of each
unscrew the lower part with the 12 connectors.
cabinet. Do not
Near the center of the backplane, note an address plug in one of the
positions marked 1, 2, or 3 on the black address strip. (Position 4 is
not used.) This indicates the cabinet number for software purposes.
The position of the plug (1, 2, or 3) should agree with the position of
the cabinet (Cabinet 1 on the bottom, etc.).
Use the CAB 1, CAB 2, and CAB 3 labels from the cable label sheets
(Figure 2-7) to label each cabinet.Position the cabinet label in the
box adjacent to connector 12 on the lower back panel. (The number
may have already been stamped by the factory.)
Stack the cabinets on top of one another on the stand. If there is
more than one cabinet, stack Cabinet 1 on the bottom arid Cabinet 3
on the top. Cabinet 1 contains the CPU/Memory (ZTN129 or
ZTN130 [R3]), and Service (ZTN85 or ZTN131 [R3]) circuit packs
(Figure 2-1 O). Do not replace the upper back panels yet.
Cabinet Contents
Check to make sure that the cabinets have been delivered with the correct
circuit packs (CPs). Table 2-B lists available CPs, their functions, and their
protectors.If the system has TN760B Tie Trunk CPs, you may also have to
set the option switches on the CPs. See “Set TN760B Option Switches” in
Appendix C for details.
November 19952-23 
						

							INSTALLATION
Table 2-B. Circuit Packs, Their Functions, and Protectors
Approved SecondaryCircuit PackFunction
Wiring Protector
N/AZTN78Supports single-line voice terminals.
(Must not be used on out-of-building
circuits, )
SCP-1 or 79ATN742Supports off-premises, out-of-
building, and bridged single-line
voice terminals.
lTW/LlNX343* I ROBZTN79Supports the 7300H Series voice
terminals used with a MERLIN®
system. (Requires local (set) power
for distances beyond 1000 feet.)
ITWILINX343* lROBTN735Supports MET sets.
N/A
TN726Supports data terminals and
computers.
N/ATN758Contains pooled modems.
SCP-1 , SCP-2, SCP-3,ZTN76Supports ground start trunks.
or LP5-230-220
SCP-1 , SCP-2, SCP-3,ZTN77
Supports bop start trunks.
or LP5-230-220
SCP-1 or 79ATN753
Supports direct inward dialing trunks.
(DID)
SCP 1 or 79ATN760BSupports tie trunks.
N/ATN763Supports auxiliary equipment.
N/A
ZTN130 (R3)Call processing/memory.
N/ATN748BTone Detector.
SCP-1 or 79ATN767Provides DS1 Interface.
N/A
ZTN131 (R3)Provides system clocks, tone
generators, detectors, and DS1
synchronization.
SCP-1 or 79ATN747E3Supports ground start or loop start
trunks.
lTW/LlNX343* I ROBTN762BSupports hybrid voice terminals.
Must be vintage 4 or later.
*Note: lROB unit ITW341 has been replaced. Use model lTW/LlNX343 only.
2-24
November 1995 
						

							INSTALLATION
Two fans are located on the left-hand front side of each cabinet. The
cabinet’s power supply is located behind the fans; to the right of the power
supply are up to 12 CPs in individual slots.Each CP is identified by a label
on the front. See Figure 2-10.
1.Remove the front cover of each cabinet.
2. Note any obviously bent or otherwise damaged circuit packs.
3. Check the CPs against the customer order. In case of irregularities
or damage, follow established notification procedures.
Danger:The System 25 cabinet contents are not user
serviceable. Some voltages inside the cabinets
are hazardous.This equipment is to be
serviced only by qualified technicians.
The CPU/Memory (ZTN129 or ZTN130 [R3]) circuit pack has two shorting
plugs that are used for factory tests (see Figure 2-1 1). They should have
been removed at the factory.
If these shorting plugs have been accidentally
left in by the factory, the system may cold start when it should warm start.
Check the CPU/Memory CP; if the plugs are present, remove them. The
shorting plugs are located on the component side of the circuit pack.
2-25 
						

							INSTALLATION
Figure 2-10.Three-Cabinet System, Front View With Covers Removed
2-26