<P> Ten - codes, officially known as ten signals, are brevity codes used to represent common phrases in voice communication, particularly by law enforcement and in Citizens Band (CB) radio transmissions . </P> <P> The codes, developed in 1937 and expanded in 1974 by the Association of Public - Safety Communications Officials - International (APCO), allow brevity and standardization of message traffic . They have historically been widely used by law enforcement officers in North America, but, due to the lack of standardization, in 2006 the U.S. federal government recommended they be discontinued in favor of everyday language . </P> <P> APCO first proposed Morse code brevity codes in the June 1935 issue of The APCO Bulletin, which were adapted from the procedure symbols of the U.S. Navy . </P>

Where does the saying ten four come from