Manual for Noncommissioned Officers and Privates of Infantry of the Army of the United States, 1917 / To be used by Engineer companies (dismounted) and Coast Artillery companies for Infantry instruction and training

by United States. War Department

Signaling with Heliograph, Flash Lantern, and Searchlight (With Shutter).

GENERAL SERVICE CODE.

26. The first position is to turn a steady flash on the receiving station. The signals are made by short and long flashes. Use a short flash for dot and a long steady flash for dash. The elements of a letter should be slightly longer than in sound signals.

27. To call a station, make its call letter until acknowledged.

28. If the call letter of a station be unknown, signal A until 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.

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.