TWO-ARM SEMAPHORE ALPHABET.

513. The semaphore alphabet is printed as the characters appear with the sender facing the receiver. Thus the character "B" is with the right arm extended horizontally.

514. Numbers shall always be spelled out.

515. The "break" and "answering" are shown in the plate. 516. Procedure signs ordinarily used are:

517. To call a ship or unit for a semaphore signal or dispatch(a) By flag hoist.-Hoist the call of the ship or unit for whom the signal or dispatch is intended, "two-blocked" (unless it is necessary to make such a call while flag signals are displayed at the same yardarm, in which case the call may be hoisted at the dip).

The unit so addressed answers by hoisting the call of the calling ship over the answering pennant (1) at the "dip" as soon as seen and until ready to receive: (2) two-blocked when ready to receive. The "attention" sign should always be made by the transmitting ship when several signalmen are sending to a large number of ships in order that the receiving signalmen may select the sender offering the best background. It should also be used when transmitting to a single ship to give the receiver an opportunity to locate the sending signalman.

1 May be used in wigwag also.

(b) Without flag hoist.-There is no equivalent for the call pennants in semaphore. When it is not practicable to call by flag hoist, and the "attention" sign is not sufficiently definite, three or four letters abbreviating the ship's name will be used as a call. To answer, the unit addressed makes the answering sign, and if that be not sufficiently definite, the three or four letters abbreviating the name of the ship answered.

SIGNALS BY SEMAPHORE.

518. The procedure prescribed for the transmission of signals by semaphore is as follows:

TRANSMITTING SHIP.

(1) Makes call, either by flag hoist and attention; by "attention" alone, or by attention followed by letter or letters abbreviating the name of the ship for whom the signal is intended.

(2) When sending to one of two ships, both of which have answered their calls and which are approximately on the same bearing, makes the letters abbreviating the name of the receiving ship. This definitely signifies to which ship the signal is being sent. It may be omitted when there is no possibility of confusion or misunderstanding.

(3) Makes break.

(4) Makes signal sign (IM). (5) Makes break.

(6) Makes signal. The names of the flags or letters and numerals are to be spelled out. The names of flags, etc., are separated by the break; complete signals are separated by the full stop. (7) Makes break.

(8) Makes "finale" sign (AR).

(9) Makes break, and waits for receiving ship to make IMI, J, or R.

(10) If a tactical signal makes IX IX several times, followed by the finale sign AR, and hauls down call (if used), as a final signal of execution. If a nontactical signal, no execute is required, makes the "finale" sign AR and hauls down call, if used.

519. Any desired degree of assurance that the signal has been received, may be attained by the use of prescribed procedure signs. Thus if the call is followed by

(a) "G," the receiving unit will repeat back.

(b) "Y," the receiving unit will acknowledge.

(c) "G" and "Y," the receiving unit will repeat back and acknowledge.

DISPATCHES BY SEMAPHORE.

520. The procedure signs prescribed for Morse are to be used in semaphore when required. When used, their position in the dispatch corresponds to their position when used in systems employing Morse.

521. The procedure prescribed for the transmission of dispatches by semaphore is as follows:

(7) When the call and answer is by flag hoist, the answering pennant is to be dipped immediately a word or sign is missed. If the call be other than by flag hoist, makes repeat (IMI). (8)

(9) Acknowledges the receipt of the dispatch (a), if the call and the answer be by flag hoist, by hauling down the answering hoist when the transmitting ship hauls down the call: (b) if the call and answer be other than by flag, makes "R."

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522. The failure to receive a word or sign is indicated:

(1) If the call and answer be by flag hoist, by the receiving unit dipping the answering pennant.

(2) If the call and answer be other than by flag hoist, by the receiving unit making the repeat sign IMI.

523. On receipt of the dispatch if the call and answer be by flag hoist, the receiving unit hauls down the answering hoist.

524. If during the sending of the dispatch, the receiving unit fails to receive any part of it for any reason such as sender becoming obscured by smoke, etc., the receiving unit should dip the answering pennant. The sending ship should then dip the call. When the receiving unit is again ready to receive, she should two-block the answering pennant. The sending ship should then two-block the call and proceed with the dispatch, starting with and repeating the last two or three words transmitted before the answering pennant was dipped.

525. If more than the last word or sign is required the appropriate procedure sign for repeating the required portion should be made.

WIGWAG.

526. Wigwag employs the International Morse Alphabet, numerals and special Morse signs. A motion through an arc of 90° to the sender's right represents a "dot," and a similar motion to the left a "dash." The only signs peculiar to wigwag are: (1) The attention" sign, i. e., the flag waved back and forward overhead and

DASH

(2) The "break" sign, i. e., a motion to the front.

576. A hand flag, a hand light, or a searchlight beam is used. The sender should face the receiver squarely. The motions for the dot and dash should be made at right angles to the line of transmission, and forthe"break" from the vertical position through an arc of 135° in the direction of the line of transmission. In order to keep the flag fully exposed the point

of the staff should be made to describe an elongated figure 8. In case a hand light is used, it is desirable to have a reference light at the