How to Read Police Scanner Codes – Step-by-Step Guide for Beginners

You’ve got your scanner tuned to the right frequency. Traffic is coming through clearly. And then you hear: “Unit 42, show me 10-8. We’ve got a 10-32 at the corner of Fifth and Main, Code 3. 10-4?”

If that sounds like a foreign language to you, don’t worry — it felt the same way to every scanner enthusiast on their first day. Police radio communication is built on a system of shorthand codes that let officers and dispatchers exchange complex information in just a few seconds. Once you learn the patterns, it all clicks into place surprisingly fast.

This step-by-step beginner’s guide will walk you through every type of code you’ll encounter on a police scanner: 10-codes, signal codes, color codes, phonetic alphabet, and plain-language dispatch. By the end, you’ll be able to follow a police radio conversation in real time.

For the full reference database of police radio codes used across the United States, visit Police Radio 10-Codes of the United States.

Step 1: Understand Why Police Use Codes

Before learning the codes themselves, it helps to understand why they exist.

Police codes were first developed in 1937 by Charles “Charlie” Hopper, communications director for the Illinois State Police, and standardized by the Association of Public-Safety Communications Officials (APCO). The goal was simple: early AM radio channels had limited bandwidth and slow push-to-talk switching. Saying “I understand your message and am proceeding to the scene immediately” ate up precious seconds and crowded the channel.

Saying “10-4, en route” achieved the same thing in under two seconds.

Codes serve several purposes beyond brevity:

• Speed — A 2-word code replaces a full sentence
• Clarity — Numeric codes cut through static better than conversational speech
• Tradition — Codes are deeply embedded in police culture and muscle memory
• Tactical privacy — Codes provide some obscurity for scanner listeners (though most codes are publicly available online)

After the 9/11 terrorist attacks, the Department of Homeland Security encouraged agencies to move toward plain language for better inter-agency communication during major incidents. As a result, many modern departments use a hybrid: plain language for complex situations, familiar codes like 10-4 for routine acknowledgments.

Step 2: Learn the 10-Code System

The 10-code system (also written as “ten codes”) is the backbone of police radio communication in the United States and many other countries. Each code starts with “10” followed by a number, and each combination has a specific meaning.

The most important thing to know as a beginner: 10-codes vary by department. A 10-33 might mean “Emergency” in one city and “Equipment needs service” in another. The list below covers the most widely shared meanings across US agencies — but always cross-reference with your local department’s specific code list.

The 20 Most Essential 10-Codes Every Beginner Should Know

The Complete 10-Code Reference for Beginners

Once you have the essentials memorized, here is the broader reference:

Step 3: Understand Response / Priority Codes (Code 1, 2, 3, 4)

Separate from 10-codes, you’ll hear priority codes (sometimes called “color codes” or “response codes”) that tell officers how urgently they need to respond to a call:

Hearing “Code 3 to the scene” means officers are responding at full emergency speed with lights and sirens — a high-priority incident. When dispatch announces “Code 4, Code 4”, it means everything is under control, and additional units can disregard.

Step 4: Understand Signal Codes

Some agencies — particularly in the southeastern United States — use signal codes instead of or alongside 10-codes. Signal codes replace the “10” prefix with “Signal”:

Signal codes are less standardized than 10-codes and vary significantly between departments. If you’re monitoring agencies in Florida, Georgia, Louisiana, or other southeastern states, you’ll encounter these regularly.

Step 5: Learn California 11-Codes (If Applicable)

California law enforcement, particularly the California Highway Patrol (CHP) and LAPD, uses 11-codes for traffic and on-scene situations. These are widely recognized in the West Coast scanner community:

As you can see from our guides on Los Angeles Police Department Codes and California Penal Codes, California’s system is uniquely layered compared to other states.

Step 6: Understand Penal Codes Used as Radio Shorthand

In California and some other states, officers frequently call out penal code numbers directly on the radio instead of describing crimes in words. If you’re scanning in California, you’ll hear these constantly:

For a full breakdown, see California Penal Codes of the United States.

Step 7: Learn the NATO Phonetic Alphabet

When officers need to spell out a name, address, or license plate over the radio, they use the NATO phonetic alphabet to avoid confusion between similar-sounding letters (like B and D, or M and N).

Example: If an officer runs a license plate “ABX 792,” you’d hear: “Alpha — Bravo — X-Ray — seven — niner — two.” (Note: “niner” is used for 9 to avoid confusion with the German word “nein” meaning no.)

For the full reference, visit the Police Phonetic Alphabet of the United States.

Step 8: Understand How a Dispatch Conversation Flows

Now that you know the building blocks, let’s put it all together by analyzing a real-world-style dispatch exchange:

Dispatch: “Unit 14, 10-20?” → Dispatch is asking Unit 14: “What is your location?”

Unit 14: “10-20 is downtown, corner of Fifth and Oak.” → Officer responds with their location.

Dispatch: “10-4, Unit 14. We have a 10-32 at 500 North Street. Respond Code 3.” → Acknowledged. There’s an armed person at 500 North Street. Respond immediately with lights and sirens.

Unit 14: “10-4, en route. 10-76 to 500 North.” → Understood. I’m on my way to 500 North Street.

(Several minutes later)

Unit 14: “10-23 at 500 North. Code 4, Code 4. Subject in custody. 10-95. Show me 10-6.” → Arrived on scene. Situation is under control, no more units needed. Suspect is in custody. I’m now busy — don’t disturb unless urgent.

Dispatch: “10-4, Unit 14. 10-95 confirmed. Show you 10-6.” → Understood. Noted.

In under 60 seconds of radio traffic, an entire incident — from report to response to resolution — has been communicated with perfect clarity. That’s the power of the code system.

Step 9: Understand Common Dispatch Phrases and Slang

Beyond formal codes, you’ll encounter recurring phrases and shorthand in dispatcher and officer speech:

Step 10: Know the Limits — What You Won’t Always Understand

Even experienced scanner enthusiasts don’t catch everything. Here’s what to expect as a beginner:

Local variations are everywhere. The same code can mean different things in different cities. The 10-Codes vs 11-Codes vs Penal Codes comparison on our site shows just how much variation exists. Always look up your local department’s specific code list to supplement the universal guide above.

Digital voice can be choppy. On P25 and other digital systems, radio traffic sometimes sounds robotic or broken up. This is a normal artifact of digital voice encoding, not poor reception.

Encryption means silence. If your local agency has encrypted their radio system, you’ll get nothing but digital static regardless of your scanner’s capabilities. This is becoming increasingly common in larger cities.

Trunked systems jump channels. On trunked systems, conversations hop between frequencies dynamically. Without proper trunk tracking, you’ll hear incomplete fragments.

Plain language is increasingly common. Post-9/11, many departments moved partially or fully to plain English for major incidents. Don’t be surprised if you hear plain conversation mixed in with codes.

Quick-Reference Cheat Sheet

Print or save this for your first sessions:

The “Must-Know” Codes:

• 10-4 = OK / Acknowledged
• 10-7 = Out of service
• 10-8 = In service
• 10-20 = Location
• 10-33 = Emergency
• 10-42 = End of watch
• 10-78 = Need backup
• 10-99 = Officer in danger
• Code 3 = Emergency response, lights and siren
• Code 4 = All clear, under control
• BOLO = Be on the lookout
• DOA = Dead on arrival

The Listen-for Pattern: [Unit called] → [10-code] → [Location or Subject] → [Response code]

Related Resources from Police Code

To deepen your knowledge of police radio communication, explore these resources on our platform:

• Police Radio 10-Codes of the United States — the full APCO standard reference
• Police Radio 11-Codes of the United States — California and West Coast-specific codes
• Other Police Scanner Codes of the United States — signal codes, color codes, and regional variants
• Why Do Police Say 10-4? — Meaning and Origin — the fascinating history of the most famous code