the  receiving  station  follows  suit  when  ready  to receive. REPETITIONS 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 repetitions. INTERRUPTIONS 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 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 relay. EXECUTIVE  METHOD The use of the executive method by semaphore is NOT  authorized. PYROTECHNICS LEARNING OBJECTIVES: State the meaning of pyrotechnics and colored lights. List the limitations and characteristics of each. PYROTECHNICS 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 these  signals. 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 weather   conditions. 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. SOUND  SIGNALING LEARNING   OBJECTIVES:  Identify procedures  for  transmitting,  receipting,  and executing  sound  signals.  Identify  limitations  of sound  signaling. 4-12