ORDERS, COMMANDS, AND SIGNALS.
[31.] Commands only are employed in drill at attention. Otherwise either a command, signal, or order is employed, as best suits the occasion, or one may be used in conjunction with another.
[32.] Signals should be freely used in instruction, in order that officers and men may readily know them. In making arm signals the saber, rifle, or headdress may be held in the hand.
[33.] Officers and men fix their attention at the first word of command, the first note of the bugle or whistle, or the first motion of the signal. A signal includes both the preparatory command and the command of execution; the movement commences as soon as the signal is understood, unless otherwise prescribed.
[34.] Except in movements executed at attention, commanders or leaders of subdivisions repeat orders, commands, or signals whenever such repetition is deemed necessary to insure prompt and correct execution.
Officers, battalion noncommissioned staff officers, platoon leaders, guides, and musicians are equipped with whistles.
The major and his staff will use a whistle of distinctive tone; the captain and company musicians a second and distinctive whistle; the platoon leaders and guides a third distinctive whistle.
(C.I.D.R., No. 15.)
[35.] Prescribed signals are limited to such as are essential as a substitute for the voice under conditions which render the voice inadequate.