A radio signal in the frequency range from 1 to 40 GHz. Numerous transmission systems use microwaves including line-of-sight between buildings and across vast distances, communications satellites, PCS cellular systems and wireless LANs. See wireless local loop and spectrum.
Early Microwave Tower
Microwaves were first used to transmit across long distances that were difficult to wire as long as line-of-sight was possible. This tower was installed in 1969 in Boulder Junction, Colorado. (Image courtesy of AT&T.)