What does 10/4 mean?

[elite]

We've all heard it before, but where does the expression 10/4 come from?

[Conti]

From the telecommunication world......police, fireman, CB operators all use 10 codes to shorten the length of transmitting time.
10-4 means message recieved...or OK
10-9 means repeat last message
10-20 means location

and so on and so on......

[Conti]

I'm sorry.....maybe i shoulda said the RADIO-COMMUNICATION world.

[elite]

I know that but why 10-4 and not say 20-4? Why were those specific numbers chosen?

[kinoons]

I dont have a clue, because someone had to pick something?

[Conti]

I have no idea. They probably wanted to use at least a 2 digit number so they wouldnt get mixed with other numbers. For instance, when a license plate such as 103-XXX is read over the radios, it is read as one-zero-three-xray-xray-xray........so if you use a two digit code, it will limit the mixups. And i assume they chose 10 because it's short and easy to pronounce...and it is the first two digit number. But that is just my WAG.

[SmackFu]

Here's the best I could do on "why 10?" From http://www.911dispatch.com/information/tencode.html:
The code is known as "the ten code" because the actual code is preceded by the word "ten." The origin and reason for this is unknown. However, it appears that the "ten" prefix was meant to signal that the numbers following are part of the code, and not an address, age, phone number, etc. Over the years, as more codes were added, the number of ten-codes ran out, and agencies began using "eleven" as a prefix. At some point, other agencies developed a nine-code that accomplished the same thing but used the number nine as a prefix.

[Arjuna34]

Here is a list of CB 10-codes (http://www.cybertron.com/~ddavis/cb10.htm). Most police departments in the US use 10-codes, but of course they're different (and police-related). Here's a sample of some police and fire 10-codes (http://www.dnaco.net/~norms/radionb.htm).

I don't know why they start with "10" though .... In amateur radio Q-codes (http://www.qsl.net/sars/q-code.htm) are used. I don't know why they start with "Q" though :)

Arjuna34

[peace]

May I venture a guess and native English speakers will decide?
Any sigle digit opening a code/sequence could be confused with a phone number sequence and/or something else. The only zip codes starting with 10... are in Manhattan, NY, and I know that they are always pronounced as one-zero-two...etc., never as ten-two-one-two or so. "Ten" is the shortest two digit number to pronounce. It still can be confused with a beginning of an address or something, but after so many years, even a rookie knows that everything starts with 'ten'.
Many years ago I bought a $0.99 sliding card in a Radio Shack called "CB Radio Code and Slang". It contained all 10-... combos.

Peace