What does 1023 mean to a cop?

10-23 is part of the "10-codes" used by police and sometimes amateur radio operators. Specifically 10-23 means to stand-by. Some other similar codes are 10-7 (out of service, or signing off), 10-8 (in service, or just signing on and standing by), and 10-10 (off duty). Probably the most well known 10-code, however, is 10-4 which is similar to the response "Roger" which means "message received."

Wednesday, February 01 2012
Source: http://www.radiolabs.com/police-codes.html