Citizens band radio
system for short-distance radio communications between individuals / From Wikipedia, the free encyclopedia
Citizens band radio (also known as CB radio) is, in many countries, a system of short-distance radio communications between individuals on a selection of 40 channels within the 27 MHz (11 m) band. Citizens band not the same as the Amateur Radio Service ("ham" radio) which has a much longer range. In many countries, CB operation does not require a license to operate. It may be used for business or personal communications.
Like many other two-way radio services, citizens band channels are shared by many users. Only one station may transmit at a time. All other stations must listen and wait for the shared channel to be available. It is customary for stations waiting to use a shared channel to broadcast the single word "break" (or "breaker") during a lull in the conversation. This lets other people using the channel know that others are waiting. In the US, channel 19 is most often used by truckers. Channel 9 is reserved for emergencies.