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I could have asked this question personally to my respected colleague who gave me a valuable answer to the question, “Is the ‘tame the infinite becoming an idiom or a popular phrase,” which I posted yesterday, but I thought this deserves an independent question.

He, the answerer gave me the comment saying, “(It’s) 10-4. Copy. That's a good example of how the phrase could be applied, and would be well-understood," to the question, “Can I say ‘the Palestinian territorial issues is an effort in trying to tame the infinite’, “which I added to the yesterday’s question.

I saw the word “10-4 copy” for the first time. So I searched for its meaning on Google, and found a certain clue from the following text in www.answerbag:

“A lot of the 10 codes are different from city to city and state to state. For example a 10-50 in Indiana is a traffic accident, but in Texas it's a murder. I personally mix and match; sometimes I say "10-4", other times I say "clear".

It seems “10-4” refers to a call sign for something. But what does it represent for? Why "10-4" is combined with "clear"? Can I say “10-4 answer /message/ report/ plan” in describing clear answer /message/ report/ plan”?

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The term " breaker, breaker" has unfortunately made its way into the mining industry. It is used when someone wants to rudely interrupt a conversation already in progress. We try and avoid these situations as it is important to hear a response to a question. –  Tarnz Mar 10 at 13:57
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4 Answers 4

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Truckers use CB radios to talk to each other during long hauls on the interstate highway system of the United States. Sometimes the chatter is just to pass the time; other times, helpful information is passed between truckers. Truckers have shorthand ways of speaking to each other over the radio, and "10-4" means "Yes, I acknowledge," similar to the way pilots and air traffic controllers use the term "Roger," and military radio operators use "Copy."

In the mid-1970's, trucker/CB lingo made its way into popular culture, spurred in part by the movie Smokey and the Bandit, and the C.W. McCall radio hit Convoy (which, if you want to hear a whole truckload of CB slang, you can listen to the song on YouTube1).

Even when it was in its heyday, most non-truckers knew very few of the "Ten Codes" (this website lists scores of them), but they did know 10-4, and they also knew the term "Breaker" (which was used to initiate a conversation one of the CB's 40 channels).

As for the Ten Codes, and why 10-10 means, "I'm done," and 10-4 means "I heard you," rather than the other way around, I'm not sure there's any particular reason. Maybe there is a reason, but that reason is closely guarded 10-35 (confidential information).

According to Wikipedia, CB is still in use today:

CB has lost much of its original appeal due to development of mobile phones, the internet and the Family Radio Service. In addition, CB may have become a victim of its own popularity; with millions of users on a finite number of frequencies during the mid-to-late 1970s and early 1980s, channels often were noisy and communication difficult. This caused a waning of interest among hobbyists.

CB radio is still used by truck drivers, and remains an effective means of obtaining information about road construction, accidents and police radar traps.

1To anyone who listened to the song: by no means do I condone crashing police barricades that are reinforced with National Guard troops at 98 MPH. In other words, don't try this near home.

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Just don't confuse the "yes" in 10-4 with the "yes" in Affirmative. The "yes" in 10-4 is just an acknowledgement, not an agreement. Affirmative indicates agreement. 10-4 just indicates that the message was acknowledged and understood. –  David Schwartz May 6 '12 at 23:09
An important point here is that the "Ten codes" did not originate with the CB, but started with police radio communications. They were co-opted by the CB radio crowd later. –  Jim May 7 '12 at 2:17
@Jim: You think I'm funny?? Funny how? Funny like a clown?? –  tenfour May 7 '12 at 10:28
A correction: "Breaker" isn't for initiating conversations. "Breaker" or "breaker breaker" is used to break in to an existing conversation. To initiate a conversation, or at least to seek a conversation partner, the jargon was "CQ" (and "CQ DX" to specifically seek a long-distance conversation). Of course when its popularity surged lots of kids started to use CBs and got all the jargon mixed up in just the way you describe it. I know this because I was a kid at the time and my dad was into CB radio and it annoyed the hell out of him when we used to say "Breaker breaker" like that (-: –  hippietrail May 7 '12 at 17:14
@hippietrail: Thanks! My knowledge of CB is limited (one can only learn so much from a Burt Reynolds movie and a novelty song). How do they say it? I know "just enough to be dangerous." I appreciate everyone who has added some more accurate details where my response may have taken the wrong exit ramp. –  J.R. May 7 '12 at 17:24
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10-4 simply means 'yes, I understand your message' in general CB (Citizen's Band) slang. Have a look at the Wikipedia page of CB slang for more.

A few of the more common CB slang phrases, including this one, made the transition into everyday speech, both in the US and further afield.

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10-4 is only an acknowledgement. It's more like "message received and understood" than "yes". (The Wikipedia page is inconsistent, in one place saying it means "acknowledged, okay", which is correct, and elsewhere saying it means "affirmative", which is incorrect. This exact same confusion with "Roger" annoys pilots and air traffic controllers alike.) –  David Schwartz May 6 '12 at 23:04
@DavidSchwartz: Speaking of Roger, what's our vector, Victor? –  J.R. May 6 '12 at 23:11
@David Schwartz. Is '10-4' and 'Roger' the same in its imprecation? –  Yoichi Oishi May 6 '12 at 23:22
Yes, they both mean "message received and understood" and are sometimes confused with affirmative which means "yes". If someone says, "Does Mary want to eat dinner with us?" and you said "10-4" or "roger", that would mean you received and understood the message, not that you had asked Mary and she did want to eat dinner with them. If you said "affirmative", that would mean that you knew that Mary did want to eat dinner with them. (These codes are specifically used over ordinary English because they are more precise.) –  David Schwartz May 6 '12 at 23:35
@YoichiOishi - Thank you for taking the correction in the spirit in which it was offered! I don't like to jump all over people's typos, but this site is all about learning to get it right - so I hoped you wouldn't mind. Fortunately, there's much less potential for embarrassment with implication/imprecation than with election/erection! I can definitely imagine that THAT must have been awkward! –  MT_Head May 8 '12 at 2:05
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The 10codes date back well before CB radio to the first use of mobile police radio in the 1930s. The 10 part doesn't mean anything and is simply there because it took a fraction of a second for the early radios to wake-up and so the first word of a message might be lost.

As to why it was ten rather than any other random number - I don't know


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In answer to your question about combining "10-4" and the term "clear," the "clear" part serves to indicate that you have finished transmitting and the channel will be clear onwards. Pretty much the same as saying "over" to indicate you are done and are deferring the open channel to your interlocutor.

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