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