PCM (see WFTD archive Pulse Code Modulation) commonly refers to digital recorders that use videotapes as the recording media, even though Pulse Code Modulation is the process by which digital data is encoded on most all types of digital recorders and CDs. This is mostly because the first decks that could handle the wide bandwidth of PCM data were video decks, and some (namely Sony’s) had PCM as part of their model names. After converting the analog signal to digital data, it is converted to a composite video signal compatible with video cassette recorders and sent to a video deck. Usually these signals were recorded on VHS or beta at the semi-pro end of things, though Beta had been more preferred for PCM because it tracked better than early VHS decks. At the pro end a U-Matic (3/4″) VCR or a 1630 PCM machine were used.
Most dedicated PCM machines and converters are old, bulky, and have been all but discontinued. They are still the preferred format by many pros, however, and most compact discs are mastered on the Sony PCM 1630, a $30,000 reference standard.