Before Signalmen can perform their jobs, they
must know the equipment with which they will work
and how to operate it. Although equipment may differ
in size or vary slightly among ships, signal gear
generally is standard throughout the Navy.
In this chapter we discuss the principles of
operation; maintenance procedures where applicable;
and safety precautions pertaining to signal lights,
infrared (IR) equipment, flags, halyards, and optical
You will not be permitted to use signal equipment
until you have been instructed in the operation of it.
The necessary permission must come from the
communications (or signal) officer or the petty officer
in charge of the signal bridge.
You must be able to locate, even under conditions
of total darkness, all light switches for electrical visual
signal equipment. Usually this is simply a matter of
familiarization. On the signal bridge most switches are
on or within reach of the equipment. When you first
report aboard ship, explore the bridge to see where the
signal equipment switch panels are located. Do this
before your watch. This practice will prove helpful
later when you are scheduled for night watches.
LEARNING OBJECTIVES: Describe the
different types of signaling searchlights.
Identify their parts and assemblies and explain
Searchlights are placed aboard naval ships for two
purposes: illumination and communications. The use
of a searchlight in visual communications is called the
directional method, because the light has to be pointed
at the receiver. Searchlights are classified according to
size and source. We discuss the 12-inch searchlights
in this chapter. The 12-inch light is either an
incandescent or mercury-xenon arc lamp.
Searchlights come under the cognizance of the
Naval Sea Systems Command (NAVSEASYSCOM),
and the ship's engineer officer is responsible for their
repair. That does not, however, relieve the Signalman
of the full responsibility for observing the instructions
for the proper use and routine maintenance of the
searchlights. The life of a searchlight depends upon
the care given to it. Preventive maintenance and daily
cleaning will keep your searchlight ready for instant
Searchlights used in the Navy normally use a
shutter to interrupt the light beam and permit
signaling. The patterns of light caused by the opening
and closing of the shutter are the basis for transmitting
messages by Morse code.
The 12-inch incandescent searchlight is used
primarily for signaling and secondarily for illumination.
Figure 2-1 shows a 12-inch incandescent
searchlight, consisting of the mounting bracket,
lamp-supporting yoke, and high-power (1,000-watt)
incandescent lamp housed in a drum. By use of a brace
or extension between the mounting bracket and the
yoke, the light can be swung in an arc to clear fixed
portions of the ship's structure.
Besides holding the lamp, the drum provides a
mounting for the signaling shutters. On top of the
drum are vane sights, used to aim the light. The back
Figure 2-1.12-inch incandescent searchlight.