How to Respond to 10 4

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Learn the meaning of this classic radio code

Co-authored by Eric McClure

Last Updated: December 29, 2024 Fact Checked

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What does 10-4 mean?

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How do you respond to 10-4?

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How do you use 10-4?

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Do you have to say 10-4 on the radio?

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Who uses 10-4?

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Tips

Wondering what’s actually going on when you hear “10-4” coming through the radio in a cop show? Got a new job where you’re going to be using a radio? 10-4 is just one of the 200 “ten codes,” a set of universal, formal communications used over citizens band radio (CB radio, for short). In this article, we’ll walk you through what 10-4 means, show you how to use it, and break down a few other basics of CB speak if you’re going to use a radio.

What does 10-4 mean?

10-4 is the universal CB radio code for “okay.” If you hear someone say “10-4” over the radio, it means they heard and understood what was said.

Section 1

What does 10-4 mean?

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If you’re talking to someone over a citizens band radio, known commonly as a CB radio, you’ll hear “10-4” all the time. It means “OK,” or, “Acknowledged.” You would say 10-4 whenever someone says something to you specifically.

Section 2

How do you respond to 10-4?

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If you respond at all, respond to their other comments. 10-4 is just a signal to indicate that someone understands you. You don’t need to respond to the 10-4, but if there’s anything else accompanying the message, you can 100% respond to that.^{[1]
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- For example, if you ask someone, “[Callsign you’re calling], can you keep an eye out for dangers on the road ahead?” and someone replies, “10-4, anything in particular you’re worried about?” you might say, “Thanks. I’ve got a tire with low pressure, so anything that might pop a tire, over.”
- If all the other person says is, “10-4,” you don’t need to say anything. You can say, “10-4, over” if you’d like to let them know you’re done speaking if you’d like.

Section 3

How do you use 10-4?

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1
Reply with “10-4” when someone messages you directly. Citizens band frequencies are open to the public, which means that anyone with a CB radio who happens to be in range can communicate with you. If anyone calls you for any reason, you would say “10-4” just to acknowledge that you hear them.
- In a professional setting (i.e. you work as a truck driver), you’d know if someone is messaging you when they reference your callsign.
- You do not need to reply to general messages that don’t concern you or aren’t addressed to you specifically.
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Use “10-4” to acknowledge and confirm a request. If someone asks you to do something, like look out on the road ahead for stopped vehicles, or give you the coordinates of a location, you can say “10-4” as a way of saying “I hear you, and I will do that.”
- A 10-4 on its own would signal that you’re accepting the request, just to be totally clear.
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Say “10-4, over” to let people know when you’re done talking. If you were in the middle of a back-and-forth conversation, you use the word “over” to signal that you’re done speaking. It doesn’t necessarily mean that the conversation is over, just that you don’t have anything else to say and you’re awaiting a response.
- If you did want to end the conversation, you would say, “10-4, out.” This means you understand what they said and you’re getting off of the radio or leaving.
- You never actually say “over and out” if you’re using a proper CB channel. You can totally use it casually, though!
- In more laid back environments, “10-4, Rodger” can be used in place of “10-4, over.”^{[2]
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Section 4

Do you have to say 10-4 on the radio?

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You only need to use 10-4 if your job/hobby uses ten codes. The ten codes are a set of 200 formal codes (all of which start with 10 followed by another number). The ten codes were invented in the 1930s to make it easier for people using CB radios to communicate with one another. If your job or hobby club uses the ten codes, use 10-4 instead of “affirmative” or “okay.”^{[3]
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- “Plain English” is the alternative to ten codes. If people are using regular conversational English over the radio, they’re using plain English. You don’t need to use “10-4” if people are using plain English.^{[4]
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Section 5

Who uses 10-4?

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Truckers, ambulance drivers, and police officers. Ten codes are common in these professions where you need to communicate quickly in a potential emergency situation. If a trucker has mere seconds before running into an obstacle, or a police officer needs help as quickly as possible, the ten codes make it easy to communicate complex information quickly and efficiently.^{[5]
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Research source} Other commonly used ten codes include:^{[6]
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- 10-1, which means “I’m having trouble hearing you,” and 10-2, which means, “you’re loud and clear.”
- 10-6, which is a kind way of saying, “I’m busy, please leave me alone.”
- 10-13, which is used to signify a weather report or road conditions update is coming up.
- 10-20, which is means, “My location is currently…”

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Tips

Keep your message as short as possible. If all you need to say is “10-4,” that’s all you should say.^{[7]
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Speak clearly and slowly so people understand you. It can be hard to understand someone over CB radio sometimes, and you don’t want to overcrowd the frequencies by repeating yourself all the time.

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Keep a standard NATO alphabet nearby. That’s where you use “alpha” for a, “bravo” for b, etc. If you ever need to spell something out, the NATO alphabet is the default way to do it.

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