Automatic control for video head switching

摘要

The video head changeover signal generator (30) operates in correspondence to a drum phase generating signal (DPG) and to a drum frequency generating signal (DFG) from a drum (5). To the head changeover signal generator is coupled a format detection (50), comparing the signal with a vertical sync. signal. The detector determines whether the time interval between the two signals corresponds to a preset region. A control transmits delay data and the shift instruction signal of the head changeover time point for each head according to the format detector output signal. The delay data are stored in a memory section, when the format has been satisfied.