Freebanding
Most CB radios imported into the UK during the 1970s and early 1980s were illegal in that they were capable of transmitting on frequencies not allocated for CB use in the UK. But over the years these radios, which are still available, are still widely in use. Freebanding is the term used for those who transmit outside of the legal frequency range using modes such as Single Side Band.
During the eighties and nineties when the propagation for international contact was at it highest, many illegal DX groups formed. One of the biggest DX Groups was Alfa Tango from Italy. Alfa Tango went on to create a division list where every country and island in the world had a division number attached.
In addition a calling frequency was allocated, 27.555 MHz on Upper Side Band. Now-a-days this calling frequency is used by thousands of illegal Freeband operators worldwide, and each following unwritten radio etiquette, policed by themselves entirely. All the illegal operators use call signs from differing groups and this call sign, often made up, is always preceded by the country division number as allocated by Alfa Tango DX group.
e.g.: England is 26xx, Scotland is 108xx, Wales is 163xx and Northern ireland is 68xx
Freebanding has grown to massive proportions and many Freebanders are not only CBers' but Ham operators as well, using their amateur radio sets modified to work on the 11 metre band. During sun spot cycles there can be many thousands of Freebanders operating on the 11 metre band.
Read more about this topic: CB Radio In The United Kingdom