CB is a kind of radio ordinary people can use to talk over a few kilometres, without a phone company in the middle. The letters stand for Citizens’ Band. Drivers — especially truck drivers — made it famous: a box in the cab, a microphone in the hand, and chat about traffic, weather, and the road ahead. The talk has its own slang (like “10-4” for “I understand”). It was a huge hobby in the 1970s and 1980s. You can still hear it, though much less than before, because mobile phones took most of that job. The feeling is informal, practical, a bit old-school — road talk, not office talk. The letters CB can mean other things in other rooms; this entry is the radio.