acknowledged. Each station will then turn on a steady flash and
adjust. When adjustment is satisfactory to the called station,
it will cut off its flash and the calling station will proceed
with its message.

29. If the receiver sees that the sender's mirror or light needs
adjustment, he will turn on a steady flash until answered, by a
steady flash. When the adjustment is satisfactory the receiver
will cut off his flash and the sender will resume his message.

[Illustration: THE TWO-ARM SEMAPHORE CODE.]

[Illustration: THE TWO-ARM SEMAPHORE CODE.]

30. To break the sending station for other purposes, turn on a
steady flash.

SOUND SIGNALS.

56. Sound signals made by the whistle, foghorn, bugle, trumpet,
and drum may well be used in a fog, mist, falling snow, or at
night. They may be used with the dot and dash code.

In applying the General Service Code to whistle, foghorn, bugle,
or trumpet, one short blast indicates a dot and one long blast
a dash. With the drum, one tap indicates a dot and two taps in
rapid succession a dash. Although these signals can be used with
a dot and dash code, they should be so used in connection with
a preconcerted or conventional code.

Signaling by Two-Arm Semaphore.

HAND FLAGS.

43. Signaling by the two-arm semaphore is the most rapid method
of sending spelled-out messages. It is, however, very liable to
error if the motions are slurred over or run together in an attempt
to make speed. Both arms should move rapidly and simultaneously,
but there should be a perceptible pause at the end of each letter
before making the movements for the next letter. Rapidity is
secondary to accuracy. For alphabet see pages following.

NOTE.--In making the interval the flags are crossed downward in
front of the body (just above the knees); the double interval
is the "chop-chop" signal made twice; the triple interval is
"chop-chop" signal made three times. In calling a station face
it squarely and make its call. If there is no immediate reply
wave the flags over the head to attract attention, making the call
at frequent intervals. When the sender makes "end of message" the
receiver, if message is understood, extends the flags horizontally
and waves them until the sender does the same, when both leave
their stations. Care must be taken with hand flags to hold the
staffs so as to form a prolongation of the arms.

LETTER CODES.

INFANTRY.

47. For use with General Service Code or se