Citizens Band Radio

Citizens Band Radio, radio channels used for two-way, short-distance business and personal communications. Citizens band radio, or CB radio as it is commonly known, was initiated in the United States in 1947 when the UHF (ultra-high frequency) 460-470 MHz band was opened to licensees from the general public. It was used mainly by private citizens in cars, lorries, homes, offices, and factories where a wireless telephone service was not available. By the early 1980s more than 20 million CB sets were operating on 40 channels in the United States; the trend peaked in Europe and other parts of the world a few years later. The CB fad had declined by the mid-1980s.

The most recent CB transceivers used a digital synthesis circuit with two crystals to generate the 80 basic frequencies of a 40-channel system by means of integrated-circuit silicon-chip technology.

Citizens band transmitters, which are restricted to a maximum power input of 5 watts and output of 4 watts, have ranges of up to about 24 km (15 mi).