Ten-codes, also known as ten signals, are code words used to represent common phrases in voice communication, particularly by law enforcement and in Citizens' Band (CB) radio transmissions.
The codes, developed in 1937 and expanded in 1974 by the Association of Public-Safety Communications Officials-International (APCO), allow for 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.
More information on the Wikipedia page , which gives examples of related system.
See also Q code