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 per minute. 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. Operation 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. Maintenance 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 twisting. 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 SEARCHLIGHT 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 supplied. 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 automatically ceases. 2-2