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A type of radio broadcasting that uses frequency modulation (FM) to provide high-fidelity sound over broadcast radio. The broadcast band falls within the VHF part of the radio spectrum, specifically 88 to 108 MHz. Odd numbered multiples of 100kHz are used for channel separation. With FM the voice is expressed over a carrier wave by varying its frequency, which causes FM modulation to consume more of the spectrum than AM broadcasts, which merely modulate the amplitude on a single frequency. Stereo FM broadcasting was approved by the FCC in 1961 when a system developed independently both by GE and Zenith were accepted. Although Stereo FM offered the Left and Right separation already used in recording, Stereo FM signals are more susceptible to noise and multipath distortion than are mono FM signals. This is why FM stereo receivers traditionally include a mono switch, which is useful as the signal-to-noise ratio worsens when a station becomes more distant or signal fades.