What Is a 10-4 Police Code? 10-4 Police Code

The 10-4 police code meaning for the police forces is Affirmative or Understood or Message Received.

The 10-4 police code is a common and widely recognized term used by law enforcement officers, truckers, and even civilians. In police radio communication, 10-4 simply means “Affirmative,” “Understood,” or “Message Received.” It is a way to confirm that a message has been heard and understood clearly.

The Origin of the 10-4 Police Code

The use of police codes, including 10-4, dates back to 1937, when the Association of Public-Safety Communications Officials (APCO) introduced what became known as the APCO Ten Signals. These codes were designed to make radio communication among officers more efficient, concise, and standardized. At a time when two-way radios had limited bandwidth, using short numeric codes allowed officers to communicate important information quickly without crowding the airwaves.

The 10-4 code was adopted as a simple, universal way of acknowledging receipt of a message, and it quickly became one of the most recognized police codes in use. Over the years, it has entered popular culture and is often heard in movies, television shows, and everyday speech.

What Does 10-4 Mean in Police Code?

In police lingo, 10-4 is shorthand for:

Affirmative
Message Received
Acknowledged
Understood

Whenever an officer says “10-4,” it means they have received and understood the transmission from another unit or dispatcher. It’s a way of confirming communication without needing a lengthy response.

The Enduring Popularity of the 10-4 Code

Even outside of law enforcement, the 10-4 police code has become a part of everyday American slang. Truck drivers, security personnel, and even everyday citizens sometimes use 10-4 in casual conversation to mean “Got it” or “Okay.” Its widespread recognition makes it one of the most iconic codes in the APCO system.

What Is 10-4 Police Code?

The 10-4 police code is one of the most well-known and widely used radio communication codes in law enforcement. It means “Affirmative,” “Message Received,” or “Understood.” Originally introduced as part of the APCO Ten Signals in 1937, 10-4 remains an essential part of police communication and has even found its way into popular culture.

Whether you’re curious about police communication systems or just wondering what 10-4 means, now you know—it’s the code for a simple acknowledgment that helps keep officers coordinated and informed during critical moments.

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Your Ultimate Resource for Police Codes in the USA – Learn, Understand & Explore 10-4 and Beyond

Welcome to All Police Codes – your trusted and comprehensive source for everything related to Police Codes and Signals in the United States. Whether you’re a curious citizen, a student of criminal justice, a radio enthusiast, or someone interested in emergency response communication, our website is designed to be your go-to guide for learning, discovering, and understanding police codes, including the widely recognized 10-4 Police Code.

At All Police Codes, we have created a detailed and user-friendly database of U.S. police codes, offering explanations and real-world usage of each code. Our team of dedicated researchers and communication specialists has been studying law enforcement radio codes and signal systems for years. We’ve poured that knowledge into building this resource to help anyone—just like you—get a clearer understanding of how law enforcement officers communicate swiftly and effectively in high-pressure situations.

What Are Police Codes and Why Are They Important?

Police radio codes (often called Ten-Codes or 10-Codes) are shorthand communication systems used by police officers, firefighters, EMTs, and other emergency services to relay messages quickly and clearly over two-way radios. These codes reduce miscommunication and save precious seconds during emergencies.

One of the most popular codes is the 10-4 code, which simply means “Acknowledged” or “Message received.” You’ve probably heard it in movies or police scanners: “10-4, copy that.” It’s just one example of how essential these codes are in day-to-day law enforcement operations.

Other frequently used codes include:

10-7 – Out of service
10-8 – In service
10-20 – Location
10-42 – Officer ending their tour of duty

You can listen to these codes live by using a police scanner or online scanner apps that stream local police radio traffic in real time.

History of Police Codes: From Morse Code to Modern Day

The origins of the 10-Code system date back to between 1937 and 1940. They were developed to standardize voice communication among public safety agencies. In 1974, the Association of Public-Safety Communications Officials-International (APCO) expanded and formalized the code list, making it the national standard.

Interestingly, APCO initially proposed brevity codes based on Morse code procedures, inspired by the U.S. Navy’s communication symbols. Though they began as signals used for Morse code transmissions, they evolved into the voice communication tools widely used by emergency services today.

Free Access to Police Code Information – Why We Do It

At All Police Codes, we provide this information completely free of charge. Our passion for emergency response communication systems and our deep respect for the brave individuals in law enforcement and emergency services fuel our mission. We believe in empowering the public with knowledge that fosters awareness and appreciation for the complex, high-stakes world of emergency communication.

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