An instrument for sound recording on magnetic tape, and subsequent
playback. The tape, consisting of small magnetic particles of iron oxides
on a thin plastic film base, is wound from the supply reel to the take-up
reel to the take-up reel by a rotating capstan which controls the speed.
The tape passes in turn the erase head, which by applying an alternating
field reduces the overall magnetization to zero; the recording head, and
the playback head. Cassettes contain thin tape handily
packaged, running at 17/8 in/s. The somewhat larger cartridges
contain an endless loop of tape on a single reel. Most recorders use two,
four, or more tracks side by side on the tape.
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