Many current satellites are programmed to be
phased out by a new generation of extremely high-
frequency (ehf) satellites. The military strategic
tactical and relay (MILSTAR) system is a joint
service program expected to be operational in the
communications are the preferred
communicating at short range when
weather conditions permit. In reliability and
convenience, visual communications often are the
equal of radio and under certain circumstances
are more secure than radio. For example, omni-
directional radio transmissions may be intercepted
by many undesired listeners, whereas unidirec-
tional visual signals are limited to observers
positioned along the line of sight.
Visual signaling systems include flaghoist,
flashing light, and semaphore.
Flaghoist signaling can be a rapid and accurate
communications method during daylight hours.
International alphabet flags, numbered pennants,
and special meaning flags can coordinate tactical
maneuvers and ships movements without radio
All sailors are expected to recognize everyday
flags. Sailors rely on the safety and informational
messages relayed by these flags, such as divers
in the water or captains on board, to help
them in their daily routine.
Flashing light uses visible beams (or infrared
light during tactical nighttime communications)
to transmit Morse Code letters through an on/off
method. Directional lights are pointed so that only
the addressee can read the message. Omnidirec-
tional lights may be located above the ships
superstructure for all ships within range to copy
Semaphore is a communications medium by
which persons signal with two hand flags, moving
their arms through various positions to
represent letters, numerals, and special signs.
Semaphore and flashing light can be used
interchangeably for many purposes. Semaphore
is more rapid for short-distance transmission in
clear daylight and may be used to send messages
to several addresses at once if they are in
Because of its speed,
semaphore is better adapted to the sending of
long messages than are other visual methods.
When radio silence is imposed, semaphore is
the best substitute for handling administrative
traffic. It is more secure than a light or radio
because it provides less chance for interception
by unauthorized persons.
Sound communications systems include
whistles, siren, bells, and acoustics. Ships use the
first three to transmit emergency warning signals
(such as air-raid alerts) and navigational signals
prescribed by the rules of the road. In wartime,
ships in convoy use these three systems to
communicate with each other.
An underwater sonar system called Gertrude
is part of acoustic submarine communications.
Used primarily for hailing NATO ships, it may
be used for radiotelephone or carrier-wave (c/w)
Pyrotechnics is the use of ammunition, flares,
or fireworks to signal a message or to illuminate
or mark targets. Most pyrotechnics for signaling
are of the fireworks variety. Common sources
are marine illumination cartridges, colored shell
bursts (parachute flares), aircraft parachute
flares, reman candles, and float-type flares.
The meaning of a pyrotechnic signal depends
on the color instead of the type of pyrotechnic
employed. The authorized use of pyrotechnics
for communications is, in general, limited to
The preceding discussion of naval warfare
operations demonstrates that extensive planning
is required if a mission is to be successful. When
all of the warfare components function together,