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 TM 55-1905-220-14-9
4-48. ALARM SWITCHBOARD - MAINTENANCE INSTRUCTIONS (Continued).
(b) A pilot light, PL5, is mounted on the alarm panel at the top section of the alarm switchboard.
Failure of this pilot light at any time should be checked immediately. It means either that the lamp is defective
and needs replacing, or, far more important, that the source of supply has failed and the entire alarm system is
out of service.
(c) If the system is being switched into service for the first time or has been out of service for
some time, it will be desirable to make certain that everything is in working order. This may be done as
outlined in paragraph d entitled, "Routine Tests".
(2) Alarm Operation.
(a) If the alarm bell, B, rings, examination of the unit panels will show at least one red target
displayed in the opening marked "Alarm". This red target, by means of the nameplate above it, will indicate
which equipment is affected. As soon as the location of the alarm is determined, the alarm switchboard
operator should throw the circuit test switch immediately above the exposed red target to the "Off" or Cut-Out
position. Throwing this switch will stop the alarm signal, cut the circuit affected out of the system, and restore
the rest of the system to normal operation so that it will be ready to report an alarm in any other alarm circuit.
The thrown switch and the yellow target will serve as a reference designation until the system and circuit
affected are restored to normal.
(b) This sequence of operation does not take into consideration the ship's regulations in regard
to handling alarm conditions. The time intervals may be modified to care for these regulations but in any case
the circuit affected should be cut out as soon as possible in order that the rest of the system may be restored to
normal, for the following reason. If one circuit has given an alarm a subsequent alarm on any other circuit will
be reported only by the red indicator swinging into view which, in a time of stress or excitement, might easily be
overlooked. Cutting out the circuit affected will reset the red target signal, substitute the yellow target and
restore the rest of the circuits to normal, after which, both the red indicator and the alarm bell will operate in
case of alarm in another location.
(c) When the equipment and circuit affected are restored to normal, the circuit may be switched
back into service by returning the line circuit test switch to the normal position.
(d) If one or more alarms should operate, and the examination of the equipment designated
discloses no trouble, the operation of these alarms is probably due to grounds on the circuit affected. See
paragraph e entitled, "Grounds".
4-1228
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