| 摘要 |
In a digital tape recording system for video and sound signals, in which information in each track is stored in plural sectors having synchronizing preambles that aid in synchronizing the playback of the information, special preambles containing a frequency component that is lower than normal are used for the first sector of the first track in each video frame or field. The normal and special preambles are produced by passing the binary code "...01010101..." (in the case of all but the first sector of each frame or field) or "...011011011011..." (in the case of the first sector) through a Miller Channel Code encoder to produce, in the first case, a synchronizing square wave fluctuating at one-fourth the bit presentation frequency, and in the second case, a synchronizing quare wave fluctuating at one-sixth the bit presentation frequency. Special resonant circuits associated with the playback circuitry detect the special lower frequency component and signal the precise start of a new frame or field. This signal is used for capstan synchronization, head positioning during playback, and head positioning during editing when the record, heads are used as playback heads so that they may be properly positioned to overwrite individual sectors on a track without overwriting other sectors.
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