switches for the equipment associated with the fuse to
provided with automatic fault detection, fault
the down (out of service) position.
reporting, and fault isolation aids.
If the failed fuse is associated with the ringing
The system's alarm panel displays failure alarms,
halts the processor, overrides an emergency transfer
generator or interrupter board, set the appropriate
condition, and initiates built-in processor diagnostic
transfer switch to the down position and replace the
routines. Two alarms are generated by the system, a
major alarm and a minor alarm. A major alarm usually
indicates a failure that removes a large number of
stations from service. A minor alarm is always
A lighted automatic transfer bus (ATB) alarm
indicated by a fault indicator light that helps isolate
lamp indicates that all available links are being used.
the fault. Both alarms have relay-operated circuits to
The only action that can be taken to satisfy this alarm
a remote alarm panel.
is to place any links that may be manually switched
The maintenance and administration panel
out of service, for test purposes, back into service.
executes the maintenance routines and displays the
results. It also is used to modify the system's
OFF HOOK ALARM
parameters and to monitor telephone traffic.
A lighted OFF HOOK alarm lamp indicates that
at least one link circuit is being held by an off-hook
condition for longer than 30 seconds with no valid
One of your duties as the IC room watch stander
connection being made. Check the links; the monitor
will be to isolate and clear automatic telephone
lamp on the link serving the off-hook line will be
switchboard alarms. When a malfunction occurs
during normal operation of the telephone switchboard,
You can determine the number of the line causing
a remote audible alarm will sound. When this happens,
the off-hook alarm by inspecting the crossbar switch
you should open cabinet 2 of the switchboard and
contacts, the select level contacts, and the originating
silence the audible alarm by momentarily operating
hold magnet. Find the contacts being held closed by
the ALM RESET switch located on the switch and fuse
the originating hold magnet corresponding to the link.
panel to the up position. After you silence the audible
The number of the line causing the alarm can be
alarm, check the alarm lamps (POWER, FUSE, ATB,
determined by observing the closed unit contacts and
OFF HOOK, RINGER) on the switch and fuse panel.
level selecting contacts. First move the switch for that
The source of the malfunction will be indicated by one
line to the down (out of service) position. Then move
or more of the lamps being lit. The procedures for
the busy switch for the link in trouble to the down
isolating and clearing the alarm condition(s) will be
position. This clears the link, and the busy switch may
discussed in the following paragraphs.
be returned to the up position.
A lighted POWER alarm lamp indicates a loss of
A lighted RINGER alarm lamp indicates that the
primary ac power from the main IC switchboard.
on-line ringing generator has failed. Set the RG1
Check the circuit J switch on the main IC switchboard
20HZ/RG2 switch located on the switch and fuse
for a blown fuse. If a fuse has blown, replace it. If the
panel in cabinet 2 to the appropriate position to select
new fuse blows, notify your supervisor.
the standby ringing generator.
A lighted FUSE alarm lamp indicates failure of
one of the fuses on the switch and fuse panel in either
As an IC Electrician third class, you will be
cabinet 1 or 2. Check both cabinets and look for a
required to perform routine preventive maintenance
flagged fuse. When the open fuse is located, inspect
on the switchboard. Since corrective maintenance
the associated equipment and circuitry for broken
should be performed by a qualified technician
wires or burn marks. If no obvious trouble is found,
specifically trained on this system, only preventive
replace the fuse. If the new fuse fails, set the switch or
maintenance will be discussed.