Police Radio Codes Explained — Ten-Codes, Signals, and Plain Speech

Updated July 28, 2026 · 7 min read

The first thing new listeners want is a decoder ring. The honest answer is that no single list is correct everywhere — but the structure behind the codes is consistent, and once you know it you can follow most traffic.

Ten-codes

Ten-codes were developed in the late 1930s, when radios needed a moment to key up before transmitting. Starting every phrase with "ten" meant the first syllable could be clipped without losing the message. They spread nationwide through the 1974 APCO Project 14 standard.

The widely shared ones:

The catch: 10-50 is a traffic accident in many jurisdictions and an officer needing urgent help in others. 10-70 might be a fire or a prowler. APCO's standard was widely adopted and then widely modified. A code list from a neighbouring county can be actively misleading.

Why agencies are dropping them

After the September 11 attacks, mutual-aid responses repeatedly ran into the problem that agencies working the same incident used incompatible codes. FEMA's National Incident Management System recommended plain language for multi-agency operations, and the federal government tied grant funding to compliance.

The result is that many departments now use plain speech for anything involving another agency, keeping codes only for routine internal traffic. On a modern feed you will often hear both in the same conversation.

Ten-codes are not the only system

Signal codes (Signal 7, Signal 11) are common in the South and coexist with ten-codes. They typically encode call types rather than radio procedure.

Priority or response codes describe how urgently a unit should respond, and these are close to universal:

• Code 1 — routine, no urgency, obey all traffic laws
• Code 2 — expedite, no lights or siren
• Code 3 — emergency response, lights and siren
• Code 4 — no further assistance needed, scene under control

If you learn nothing else, learn Code 3 and Code 4. They tell you when something is escalating and when it has resolved.

Penal or statute codes are numbers straight out of the state criminal code. California's 187 (homicide) is the widely known example. These are the most jurisdiction-specific of all — a number that means one offence in one state means something entirely different in another.

The phonetic alphabet (Alpha, Bravo, Charlie) spells out plate numbers and names. This one really is standard, and it is worth memorising because it appears constantly.

Common phrases you will actually hear

Plain-language phrases are increasingly the substance of a feed:

• "On scene" / "Out at" — the unit has arrived
• "Show me clear" — finished, available again
• "Start me another unit" — requesting backup
• "Copy direct" — dispatcher heard the unit's own transmission
• "Be advised" — information the unit should have before arriving
• "Signal 100" or "emergency traffic" — clear the channel, everyone else stand by
• "Negative contact" — searched, found nobody
• "Unfounded" — the reported situation did not exist

How to learn your local codes

1. Find the agency's own list. Many departments publish their radio procedure manual, and public-records requests often turn one up.
2. Listen for repetition. Dispatch repeats call types constantly. A code you hear ten times in an hour followed by "on scene" within a few minutes is almost certainly a routine service call.
3. Cross-reference with the incident. If a code is followed by a fire response and an EMS unit, you can infer the category without a list.
4. Check regional forums. Local scanner communities maintain code lists more accurate than any national compilation.

A note on what you are hearing

Dispatch traffic is preliminary and often wrong. A "shots fired" call becomes fireworks. A reported break-in becomes a resident who lost their key. Officers speak in shorthand about situations they have not yet seen, involving people who have not been charged with anything.

Treat it as what it is: an operational conversation you happen to be able to overhear, not a news report.

If your local channels have gone silent, encryption is the usual reason — see why police channels are encrypted. For whether you are allowed to listen at all, see is it legal to listen to a police scanner.