A police code is a brevity code, usually numerical or alphanumerical, used to transmit information between law enforcement over police radio systems in the United States. Examples of police codes include "10 codes" (such as 10-4 for "okay" or "acknowledged"—sometimes written X4 or X-4), signals, incident codes, response codes, or other status codes. These code types may be used in the same sentence to describe specific aspects of a situation.

Codes vary by state, county, and agency. It is rare to find two agencies with the same ten codes, signals, incident codes, or other status codes. While agencies with adjacent or overlapping jurisdictions often have similar codes, it is not uncommon to find differences even within one county or city. Different agencies can have codes dissimilar enough to make communication difficult. There are similarities among popular sets of 10-codes.^[1]

The topic of standardized codes has been discussed in U.S. law enforcement circles, but there is no consensus on the issue. Some law enforcement agencies use “plain talk” or “plain codes” which replace codes with standard speech and terminology, albeit in a structured manner or format. Arguments against plain language include its lack of brevity, variability, and lack of secrecy which is often tactically advantageous or a safety issue when officer communications can be overheard by the civilian public.^[2]

The Hundred Code is a three-digit police code system.^[3] This code is usually pronounced digit-by-digit, using a radio alphabet for any letters, as 505 "five zero five" or 207A "two zero seven Alpha". The following codes are used in California. They are from the California Penal Code except where noted below.^[4]

In the 1970s, the television show Adam-12 was considered so authentic in its portrayal of Los Angeles PD officers and their procedures that excerpts from the shows were used as police training films around the country.^[5] This led to widespread use of California Penal Codes as radio codes.^{[citation needed]}

"500" codes are only radio codes that substitute for other code sections. For example, a "503" is not Penal Code section 503 (embezzlement). All of the "500" codes, generally, involve vehicles and are thus grouped together (except 594, which is an actual Penal Code section). Additionally, "390" and variants are also radio codes only (CPC 647(f) is the legally enforced section "public intoxication").

In California, some radio codes in the 400–599 range that refer to vehicle violations are left over from the California Vehicle Code (CVC) which was revised in 1971. Some agencies, such as the California Highway Patrol (CHP) use the current vehicle code numbers while municipal and county police agencies, especially the Los Angeles Police Department (LAPD) still use the 500 series.

• Emergency service response codes
• APCO phonetic alphabet
• ICAO spelling alphabet
• Ten-code

• "Police Scanner Codes Site". PoliceCodes.org.
• "Radio and Identification codes". Mendosa.com.
• "Police Codes". PoliceCodes.net.