Citizens Band Radio

A short-range, license-free-in-most-countries, two-way land mobile radio service operating near 27 MHz; CB radios share a small number of channels among many users, who take turns transmitting with a push-to-talk button, typically at power limits of 4 watts for AM or FM and 12 watts for single-sideband transmission. The United States Federal Communications Commission created the personal radio service in 1945, and the modern Class D citizens band launched on September 11, 1958 at 27 MHz with 23 channels, later expanded to 40 channels in 1977. CB usage peaked in the 1970s, when truck drivers adopted it heavily after the 1973 oil crisis to locate fuel and warn each other of speed traps, a boom that inspired films, television shows and novelty songs; individual licensing in the United States ended in 1983, and CB radio today is used mainly by hobbyists and by truckers relaying traffic and roadside conditions.