In the late 1970s to early 1980s, there was a frenzy for Citizens Band (CB) radio in the UK. However, while it was legal to own such a device, it was not legal to operate on the airwaves. So an elaborate system of codes and pseudonyms were used by the “breakers” who communicated across miles to neighbor hobbyists and strangers.

Link: https://hyperallergic.com/417878/eyeball-cards-cb-radio-culture/