ATT System 25 Installation And Maintenance Manual

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2.
3.
4.
If you hear dial tone, continue with this test.
Dial the digits 1234567890 *#.
Y
OU should hear a DTMF signal as each key is pressed.
If the test passes, you will hear dial tone within 1 to 3
seconds after you enter #.
Repeat the test for each touch-tone receiver.
Replace the Service Circuit CP if this test fails.
7300H Series Terminal Troubles
Symptoms:
7300H Series terminal LEDs and/or tones not functioning properly.
Procedures:
1.Move the T/P lever on the left-hand side to the “T” (Test) position,
and hold it there.
2. Release
3. If any
Symptoms:
Voice
Tone ringing should be heard.
All the red and
alternately while
the lever, letting
green LEDs on the terminal should flash
the lever is held in this position.
it return to its normal position.
Ringing tone should be silenced, and the LEDs should be
dark.
part of the test fails, replace the terminal.
terminal keys don’t click.
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Procedures:
1.Make sure that the appropriate ZTN79 CP is translated.
2. Check for the presence of -48 volts at test point on front of cabinet.
Symptoms:
Inoperative
used.
Procedures:
1.If LOCALdisplay-equippedvoice terminal when LOCAL button isbutton/lamp
activate LOCAL button.is off, and voice terminal is inoperative,
2. If terminal is still inoperative, check for other problems.
Virtual Facilities Troubles
Refer to Figure 4-12 for assistancein clearing virtual facilities troubles.
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Figure 4-12.Clearing Virtual Facilities Troubles (Sheet 1 of 3) 
						

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Figure 4-12.
Clearing Virtual Facilities Troubles (Sheet 2 of 3)
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Figure 4-12.Clearing Virtual Facilities Troubles (Sheet 3 of 3)
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Trunk Troubles
Many trunk troubles originate in the central office (CO) facilities. The first step
in identifying trunk troubles should be to check for presence of dial tone at
the Trunk Access Equipment (TAE). If required, check the Error Log records,
and make a trunk test call.
Note that it is sometimes difficult for the user to detect or identify trunk
troubles. If an outgoing trunk is down, an error is recorded in the error log
and the trunk is taken out of service (see Note ). If an incoming-only trunk is
down, however, the only indication of trouble is customer complaints that
incoming calls are not being received.
Note:For Release 1, Version 2 or Release 3 systems, the system
will not busy out more than half of the trunks in any pool.
Thus, a permanent alarm may be logged against a particular
trunk, but the trunk may not be taken out of service because
.of this constraint.
Other troubles could occur because of incorrect loop current. The loop
current of trunks from the CO to System 25 should be 20 mA.
Outgoing Trunk Problems
Symptoms:
Difficulty in seizing outgoing trunks.
Procedures:
1.
2.
3.
4.Verify that dial tone is received from the CO at the TAE (see Note).
If dial tone is not present, notify the CO through the proper channels.
Note:
For ground-start trunks, apply ground to the Ring
lead to get dial tone.
Go off-hook at a test
Dial *2 (the test code
Dial the 4-digit trunk
same number used
trunk.)station to get system dial tone.
for all non-DID facility trunks).
number of the trunk to be tested.
by the System Administrator to
(This is the
identify this
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5.Listen for dial tone from the accessed trunk. If dial tone is not
present, isolate the fault to a trunk port CP or location in the trunk
access equipment, etc., using a test set.
6.If dial tone is present, dial a working outside number. Verify that the
call is complete.
7.If trunk is busy, fast busy tone is heard. If a nonport trunk was
dialed, fast busy tone is heard.
Incoming Trunk Problems
Symptoms:
Incoming trunks (of any type) not working properly.
Procedures:
1.Place an incoming call through the troubled trunk.
2. At the SAT, check the trunk translations to be sure this trunk has
been properly translated. (See the Administration Manual.)
Error Log Interpretation: Loop-Start Trunks
Procedures:
1.
2.
3.
4.
5.
Check Error Log for messages pertaining to loop-start trunks.
If “no loop current on incoming call” is displayed, no loop current
was detected on an incoming call.The CP detected ringing, but not
loop current when it closed the loop. In this case, the CO facility is
probably good, but either the current sensor on the CP is faulty or
the CO battery circuit is faulty.
Switch trunk ports, and see if the problem moves to the new loop-
start trunk.
If the problem does not move, the loop-start CP is faulty and must
be replaced.
If the problem moves, the fault is with the CO. Notify CO personnel
through the proper channels.
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6. If “no loop current on outgoing call” is displayed, either of the above
conditions could be true. It is more likely, however, that the facility is
down.
7.Place an outside call on the line using the trunk test call procedures
listed in outgoing Trunk Problems.If you get fast busy tone, switch
trunk ports and try again.
8. If the problem does not move, replace the Loop Start CP.
9. If the problem moves, the fault is with the CO. Notify CO personnel
through the proper channels.
Error Log Interpretation: Ground-Start Trunks
Procedures:
1.
2.
3.
4.
5.
6.
7.
Check the Error Log for messages pertaining to ground-start trunks.
If “no loop current on incoming call” is displayed, no loop current
was detected on an incoming call. The CP detected ringing, but not
loop current when it closed the loop. In this case, the CO facility is
probably good, but either the current sensor on the CP is faulty or
the CO battery circuit is faulty.
Switch trunk ports and see if the problem moves to the new ground-
start trunk.
If the problem does not move, replace the Ground Start CP. 
If the problem moves, the fault is with the CO. Notify CO personnel
through the proper channels.
If “fault on outgoing seizure”is displayed, either of the two
conditions is true. The first condition is that the trunk CP did not
detect loop current as in the case of the “no loop current on
incoming call” message.
The second condition is that the trunk CP
did not detect tip ground.This could be either a problem with the
CO or the ground detector on the CP.
Place an outside call on the line using the trunk test call procedures
listed under Outgoing Trunk Problems. If you get fast busy tone,
switch trunk circuits and try again.
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8.
9.
10.
11.
12.If the problem does not move, replace the Ground Start CP.
If the problem moves, the fault is with the CO. Notify CO personnel
through the proper channels.
If “Ringing no ground”is displayed, the T and R leads may be
reversed in the trunk access wiring. The T lead should have ground,
and the R lead should have –48 volts. These can be verified by
reversing the ground and ring leads and checking with either a
voltmeter or a test set (with a polarity switch). A voltmeter should
indicate the presence
when the Ring lead is
“Ringing no ground”
on the Ground Start
necessary.
Ringing no ground”
of 48 volts. A test set should provide dial tone
temporarily grounded.
may also mean that the ground detect circuit
CP is faulty. Check and replace this CP if
may also mean that the CO is unable to send
ground. If this is the problem, notify the CO through the proper
channels.
DID Trunks Troubles
Symptoms:
User complaints that DID trunks are not operating properly (for
example, callers hear ringing, but users do not hear ringing at voice
terminals).
Procedures:
1.Check the trunk translations via the SAT to be sure that trunks have
been properly translated. (See the Administration Manual.)
2. Check the Error Log for messages such as:
lRotary dial
lRotary dial
lRotary dialbefore wink
pulse too earlypulse during wink
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3.
4.
5.
6.
7.
8.
9.
l CO failure to release after PBX disconnect
l CO belated release.
These messages indicate CO problems. The first three errors are
very common when DID trunks are installed. The CO should be
notified through the proper channels about any of these problems.
The CO failure to release after PBX disconnect can frequently be
corrected by disconnecting and then reconnecting the DID trunk. If
this procedure does not resolve the problem, notify the CO through
the proper channels.
Check each DID trunk port suspected of being faulty by dialing in
with the touch-tone test set beginning at the network interface. (Be
sure to use the appropriate dialing mode, dial pulse or rotary.)
If the test call is successful at the network interface, the fault is
probably with the CO facility, and the CO should be notified through
the proper channels.
If the test call 
is not successful at the network interface, repeat this
test at the cabinet.
If the test fails at the cabinet, replace the DID circuit pack.
If the test call is successful at the cabinet but not at the network
interface, repair the trunk access equipment wiring.
Check the Error Log for any messages indicating unused
(inaccessible) DID trunks.
Switched 
Loop Attendant Console Troubles
Refer to Figure 4-13 for assistance in clearing Switched Loop Attendant
Console troubles.
Note:If problems occur after the LOCAL mode has been used,
activate the LOCAL mode again and recheck console
operation.
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