Signal Modulation
Composite video can easily be directed to any broadcast channel simply by modulating the proper RF carrier frequency with it. Most home analog video equipment record a signal in (roughly) composite format: LaserDiscs store a true composite signal, while consumer videotape formats (including VHS and Betamax) and lesser commercial and industrial tape formats (including U-Matic) use modified composite signals (generally known as "color-under"). On playback, these devices often give the user the option to output the baseband signal or to modulate it onto a VHF or UHF frequency compatible with a TV tuner (i.e., appearing on a selected TV channel). The professional television production uncompressed digital video videocassette format known as D-2 (video) directly records and reproduces standard NTSC composite video signals, using PCM encoding of the analog signal on the magnetic tape.
Read more about this topic: Composite Video
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