Police codes are signals used by law enforcement officials to communicate in two-way radio communications. The codes are numbers that represent words, phrases, or messages. Police 10 codes were used in the United States law enforcement community before the Second World War. In 1940, the Association of Public Safety Communication Officials (APC) published the first official set of police 10 codes. These radio signals were invented to help reduce the use of speech on the police radio and enable a certain amount of privacy to radio transmissions. However, there is no genuinely universal or official set of police 10 codes, and the meaning of a particular scanner code or signal can vary between one police jurisdiction and another.
Regarding the specific code "101," it appears to have different meanings depending on the source. According to one source, "101" means "Ending security check". Another source lists "10-101" as a question, meaning "What is your status?". It is important to note that police codes can vary between jurisdictions, so the meaning of "101" may differ depending on the location.
