Ampex Corporation

Edwin S Busby, Jr

Reginald W Oldershaw

A tape speed measuring circuit for use with quadruplex video recorder/reproducers, which identifies the speed at which the recording was made to allow automatically switching to the correct speed upon playback. The circuit measures the ratio of control track frequency relative to the capstan tach frequency to obtain the recorded tape speed. A commutating filter means responsive to the capstan tach signal allows the accurate extraction of the desired control track signal component at all tape speeds. Divider means counts the number of tach pulses received during a selected time period. If the number of pulses is more or less than a pre-selected quantity, a high or low logic level respectively is generated commensurate with the standard 15 or 71/2 inches/second recorded tape speed.

Method and apparatus for measuring the speed at which a tape was recorded

An error corrector circuit for correcting a tape timer in a video tape recorder/reproducer (VTR) having a multiple frequency control track, wherein a selected control track frequency is separated from the composite frequencies via commutating filter means capable of following frequency variations caused by variable tape speeds. The resulting filtered control track signal of selected frequency is phase compared with a tach clock signal of similar frequency obtained from the capstan tachometer. In the absence of slip, creep, tension variations, and other speed errors caused by playing the tape on different devices, there is no phase difference between the compared signals, which are thus phase locked together. Any phase deviations between the filtered control signal and the tach clock signal are detected and fed back to correct the tach clock signal so that it accurately represents the passage of tape past the VTR head means. A television frame rate pulse output derived from the corrected tach clock signal is fed to the tape timer of the VTR.

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Menlo Park, CA, United States of America

Edwin S Busby, Jr