If you’ve ever watched a police procedural or action movie, you’ve likely heard the phrase “10-4” used on a police radio. But what does it mean exactly? In the following sections, we’ll take a closer look at the history of ten-codes and explore some of the other codes that are commonly used in emergency situations.

10-4 Meaning – Created by Englishstudyonline
10-4 Meaning
What Does 10-4 Mean?
In short, “10-4” is a code used to acknowledge a message or confirm that it was received. It’s a part of a system of codes known as “ten-codes” that were developed for use in radio communications by emergency services and law enforcement agencies.
The code “10-4” specifically means “affirmative” or “OK.” It’s a way of letting the other person know that you received their message and understood it.
It’s worth noting that ten-codes are not universal and can vary between different agencies and regions. However, “10-4” is one of the most widely recognized and commonly used codes.
Origin of 10-4
“10-4” is actually part of a set of radio codes called “ten-codes” that were invented by the Association of Public-Safety Communications Officials-International (APCO) in the 1940s. These codes were used to help standardize radio communication between different agencies and jurisdictions.
The specific meaning of “10-4” is “message received” or “OK”. It’s an affirmative signal that lets the sender know their message was understood. The code became popular in the 1950s through the TV show “Highway Patrol”, where the main character would often use “10-4” in his radio communications.
Interestingly, the use of ten-codes has declined in recent years, as many agencies have switched to plain English communication. However, “10-4” remains a cultural icon and is still used in certain situations, such as by truckers on their CB radios.
Who Uses 10-4?
“10-4” is used by several groups, primarily in settings where clear and concise communication is crucial:
- Law Enforcement Agencies: Police officers use “10-4” in radio communications to acknowledge messages.
- Emergency Services: Firefighters and emergency medical services (EMS) personnel use it to confirm receiving instructions or information.
- Truck Drivers and Other CB Radio Users: It’s common in the trucking industry and among other citizens band (CB) radio users for acknowledging messages during their communications.
- Military Personnel: In some contexts, military forces may use “10-4” and other ten-codes for concise radio communications.
Examples of 10-4
Example 1:
- Dispatcher: “Unit 5, proceed to Main Street for traffic control.”
- Officer: “10-4, en route.”
Example 2:
- Person A (via radio): “Can you hear me clearly now?”
- Person B: “10-4, loud and clear.”
Example 3:
- Supervisor: “Make sure to secure the area and report back when it’s done.”
- Employee: “10-4, I’ll call in when it’s complete.”
Example 4:
- Friend (on walkie-talkie): “Let’s meet by the park entrance in 10 minutes.”
- You: “10-4, see you there.”
Synonyms for 10-4
Here are some synonyms and similar phrases used to convey the same meaning:
- Affirmative
- Understood
- Roger
- Copy
- Got it
- Acknowledged
- Roger that
- Received
- OK
- Yes
Related Terms to 10-4
Here’s a list of terms related to “10-4”:
- CB Radio – Citizen’s Band radio, a system of short-distance radio communications between individuals typically on a selection of 40 channels within the 27 MHz (11 m) band.
- Two-way radio – A radio system that allows for bidirectional voice communication between individuals.
- Radio check – A query or test to determine if a radio is transmitting and receiving properly.
- Roger – Another radio communication term that means received and understood (similar to 10-4).
- Over and out – Phrase used to indicate that a conversation is finished and the channel is being cleared.
- Copy that – Synonymous with 10-4, used to confirm receipt and understanding of a message.
- Breaker – Used in CB radio communications to signal the desire to begin transmission on a channel.
- Ten codes – A numerical code system used in voice communications, particularly by law enforcement and in CB slang.
- Affirmative – A formal way to say “yes” or to agree with something in radio communications.
- Handle – A nickname used instead of a real name to identify the speaker during CB radio communications.
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