Figure 2-5.—Multipurpose signal light.
For signaling, the light may be held in the hand
and operated with the trigger. It has an effective
signaling range of 4,000 yards and is designed to send
up to 12 words per minute.
YARDARM BLINKERS SYSTEM
LEARNING OBJECTIVE: Explain the function
of the yardarm blinkers system.
Yardarm blinkers are 32-point, 360-degree white
lights located on the yardarm or on separate supports
on the mast. (See fig. 2-6.) The fixtures are spraytight
and fitted with screens at their bases to prevent glare
or reflection, which could interfere with navigation.
The range of the yardarm blinkers is limited and can
only be used effectively during hours of darkness.
Figure 2-6.—Yardarm blinkers.
Yardarm blinkers permit communication to
several units simultaneously. These lights are operated
from signal keys located on each side of the signal
bridge and in the signal shelter. By selecting the
appropriate position on the transmitter control panel,
you can operate the beacons as a steady light or as
blinkers using the signal key.
Normally, maintenance is the responsibility of the
Electrician's Mates. Cleanliness and upkeep of the
light exteriors are tasks for Signalmen. This upkeep
can be hazardous. Before going aloft, check Man Aloft
Procedures covered later in this chapter.
INFRARED COMMUNICATION
EQUIPMENT
LEARNING OBJECTIVE: Explain the function
of infrared (IR) transmitting sets.
Infrared equipment consists of the AN/SAT 2 IR
transmitting set or a searchlight fitted with an H hood.
This equipment is popularly known as Nancy gear.
Night vision sights (NVSs) make it possible to
visually detect the invisible IR rays of the light
spectrum. Together this equipment provides a measure
of communication security.
Like visible light, IR is limited in range to the
horizon, and range is further reduced by adverse
weather conditions.
AN/SAT 2 TRANSMITTING SET
The AN/SAT 2 IR transmitting set (see fig. 2-7) is
designed to transmit signals in the IR region of the
frequency spectrum; that is, between 0.75 and 1.2
microns. Infrared radiations are invisible, thus
providing a secure means for signaling at night under
darkened ship conditions. The two IR transmitters
(beacons) may be operated as a steady source for
point-of-train purposes, or they may be flashed in
Morse code for signaling and recognition. The
beacons are visible for 360 degrees and can be
positioned to transmit fore and aft or port and
starboard. For security, the beacons have been
designed so they cannot be detected by the unaided
eye at distances greater than 400 yards. The beacons
are white-light tight; however, they are visible as dim
red lights at short distances. The AN/SAT 2 is used
mainly for nondirectional communication.
2-6
