!0-4 Good Buddy, again

So what the heck's 10-4 – and is there a 10-1, 10-2 or even 10-99 [yes, there is]? Ten-codes were developed by the Association of Public-Safety Communications Officials-International (APCO) in the US to represent common phrases used in radio communications, such as Citizens' Band (CB) radio. Click here for a complete list of 10 codes.