door is hinged, allowing access to the drum interior.
The parabolic reflector is mounted on the rear door.
Signaling levers on both sides of the drum open and
close the shutters to permit signaling up to 15 words
The drum is mounted on the yoke with trunion
bearings so that the light can be elevated or depressed.
Locking clamps on the yoke secure the light in
elevation; locking clamps beneath the mounting
bracket lock the light in train.
There is very little to operating this type of light.
You can learn in a short time the proper procedure for
turning the lamp on and off, positioning it horizontally
or vertically, and operating the shutter. Train the
searchlight directly on the receiver in daytime, but not
at night, for it might blind the receiver and bridge
personnel. At night, train the searchlight slightly
under or above the receiver.
A remotely mounted rotary switch controls power
to the searchlight. To open the signaling shutters, use
pressure on the signaling lever to overcome spring
pressure. When you release pressure on the signaling
lever, the spring forces the shutters closed. Two leather
bumpers cushion the return of the signaling lever,
protecting the shutter from damage.
Do not keep the searchlight switched on longer
than necessary. When the searchlight is not in use, lock
it in the fore-and-aft position.
When the signal bridge is secured, as during
overhaul, searchlight lay-up maintenance should be
conducted according to the maintenance requirement
card (MRC); also, all tests and care and maintenance
procedures should be performed before redeployment,
to ensure proper operation. During inclement weather,
place a protective canvas cover over lights not in use.
Maintain searchlights according to current MRCs.
Electrical contacts must be kept clean and bright.
Electrical leads should be checked daily and replaced
as soon as defects appear. Depending on the amount
of time they are used, moving parts such as trunion
bearings and stanchion sockets must be lubricated at
intervals. Shutter vane hinges and links should be
lubricated once a quarter, or more frequently if
required. Searchlights should be operated for a few
minutes after lubrication with the door glass and cover
removed to allow the lubricant to evaporate.
Screws and bolts should be checked for tightness
at regular intervals, particularly following the firing of
the ship's guns.
The two shutter stop screws should be adjusted at
regular intervals to take up the wear in the leather
bumpers. The leather bumper should just touch the
stop adjustment when the vanes are closed to prevent
The reflector should be cleaned quarterly and/or
when needed. Refer to your MRC for instructions on
cleaning the reflector.
Never paint a bearing surface or the working
member of any part of the light. Do not paint bolts,
locking nuts, or other parts accessing the interior. Do
not paint over nameplates, and keep oiling cups and
holes free of paint.
Replacing the lamp and focusing should be done
only by qualified Electrician's Mates unless a member
of the signal gang is qualified and authorized to do so.
12-INCH MERCURY-XENON ARC
The mercury-xenon arc searchlight uses a
1,000-watt mercury-xenon lamp. The searchlight is
provided with an automatic lamp-starting circuit.
Parts consist of a drum, back dome, signaling
shutter, mounting yoke, lamp, focusing device, starter
box, and ballast assembly. The automatic starting
circuit assembly is attached to the lower part of the
drum. A screening hood with various color filters is
A high-voltage, pulse-type circuit is used. When
the searchlight is turned on, the boost transformer
supplies 130 volts to the primary coil of the
transformer, which in turn provides a series of pulses
of approximately 50,000 volts generated by
high-frequency discharges through a spark gap.
When the main arc in the lamp is established, the
voltage to the primary coil of the transformer drops to
65 volts. This voltage is not high enough to cause the
secondary voltage of the transformer to break down
the spark gap. Thus, the high-voltage pulse to the lamp