A New Technique for Time-Base Stabilization of Video Recorders

Videotape recorders in professional broadcasting use require electronic time-base correcting devices to stabilize the timing of the output signal to the accuracy needed by color television. Many schemes have been used or proposed for this purpose. The method described is arranged to provide an unusually large operating range, thereby permitting its associated recorder to be designed for fast starting time, quick recovery from large disturbances, and fully synchronous operation. The technique involves the use of switched fixed ultrasonic delay lines whose delay times are arranged in a binary order, followed by a conventional continuously variable vernier delay line. A new method of direct measurement of velocity errors is incorporated in the system.