The purpose of "Visual Signals" (TC 3-21.60/FM 21-60), is to standardize visual signals and to serve as a training reference. It is a guide. It does not cover all visual signals used in the Army, only those that are commonly used. Signals used with equipment or during operations are in manuals that relate to such operations. Efficient combat operations depend on clear, accurate, and secure communication among ground units, Army aviation, and supporting Air Force elements. Control and coordination are achieved by the most rapid means of communication available between Soldiers and units. When electrical and/or digital means of communication are inadequate, or not available, a station-to-station system of visual communication is an alternate means for transmitting orders, information, or requests for aid or support. Through the use of hand-and-arm signals, flags, pyrotechnics, and other visual aids, messages may be transmitted. Although many of these signals are widely used, incorporated into unit communications-electronics operating instructions and standing operating procedures, Army-wide standardization will increase their effectiveness.