the receiving station follows suit when ready to
Receiving stations request repetitions only when
the transmitting station completes the message. The
procedure to request repetitions by semaphore is
basically the same as for flashing light. Chapter 4 of
ACP 129 contains procedures for receiving and giving
The transmitting station may dip the call sign of
the receiving station to indicate that it is required to
wait. The receiving station should then dip its
answering hoist until the transmitting station again
hoists the call sign close up. The transmitting station
may also use the prosign AS by semaphore. The
receiving station may dip the answering hoist to
indicate that it is unable to receive.
Relay procedures are basically the same as those
for flashing light except that the relay station need not
wait for the end of the message before beginning to
The use of the executive method by semaphore is
LEARNING OBJECTIVES: State the meaning
of pyrotechnics and colored lights. List the
limitations and characteristics of each.
Pyrotechnic signals are contained in Pyrotechnic
Signals, ACP 168. Pyrotechnic light, flares, and
rockets for international emergency situations are
found in the Intemational Code of Signals, Pub 102.
The meaning of a pyrotechnic signal depends on the
color rather than the type of pyrotechnic used. Limitations
of pyrotechnic signals must be fully recognized by
Signalmen. Following are some characteristics that serve
as guidelines for using pyrotechnics:
1. Simplicity, instead of complicated color
combinations, is essential. Signals composed of a
succession of pyrotechnics or a combination of colors
should be avoided because there is always danger that
an observer may not see the whole signal and,
consequently, may misinterpret it.
2. Experiments have proved that the standard colors
red, white (or yellow), and green are the only satisfactory
colors under varying conditions of visibility.
3. Under certain atmospheric conditions, white
signals may appear yellow. Likewise, a white signal
may be mistaken for a green signal under certain humid
conditions. It is easy for tracer signals to be confused
with red ones. Therefore, take care when identifying
4. Pyrotechnic signals are easily copied by the
enemy, either for their own purposes or to confuse their
opponents. Little reliance can be placed on them unless
the source or origin can be definitely identifed.
5. At a distance, it is difficult to identify the exact
location from which a pyrotechnic was fired. A single
pyrotechnic fired by each of two separate originators
may appear to an observer as two pyrotechnics fired
simultaneously or in succession from one originator.
6. The originator of a pyrotechnic signal has no
way of knowing whether the signal was observed by
the receiver for whom it was intended. Unless the
action taken by the receiver indicates receipt, the
signal should be confirmed by other means of
communication. Once a pyrotechnic signal has been
fired, there is no method of canceling except by using
a different pyrotechnic device or by some other
method of communication.
7. The range of visibility for a pyrotechnic signal
is variable and unreliable because it depends largely on
Pyrotechnic signals may be used either by day or
night unless otherwise specified. Being a Signalman,
you must be very familiar with pyrotechnic signals;
one day you will serve as a boatcrew Signalman. One
of your duties as a member of a boatcrew is identifying
the different pyrotechnic signals.
LEARNING OBJECTIVES: Identify
procedures for transmitting, receipting, and
executing sound signals. Identify limitations of