A list of codes used on a live police scanner is available on websites such as radiolabs.com and zipscanners.com. These websites provide users with comprehensive lists of codes used by live police scanners together with their meaning.
Police forces have been using codes for emergency communication since the 1920s. The purpose of the codes was to make communication fast and efficient. Police codes vary from one state to another, and even from one county to another. Some common codes include 10-0 for caution, 10-4 for message received, 10-26 for clear, 11-79 for accident with ambulance sent and 11-99 for officer needing help.