| 摘要 |
<p>PURPOSE:To simplify constitution of a controlling device and reduce cost by phase comparing a rotation phase detection signal obtained at every 1.5 rotation of a rotary head of VTR of 4 head system and vertical synchronizing signal of recording video signals directly. CONSTITUTION:A rotary cylinder carrying 4 heads is rotated by a motor 11, and phase and speed of the motor 11 are detected by a rotary head phase detector 12 and a rotary head speed detector 13 respectively. Signals at every one rotation of a drum from the detector 12 are waveform shaped 14, trisected 15 and delayed 16, and 1/3 PGD signal is inputted to the reset terminal of a counting circuit 17. The speed signal of the detector 13 is waveform shaped 18, counted by the circuit 17 and a signal 1/30 FG is outputted. The signal 1/30 FG is processed by a 1/2 dividing circuit 19, a delay circuit 20 and D-FF 21, and signals SW0 are outputted at every 1.5 rotation of the head. The signals SW0 and vertical synchronizing signals of video signals are phase compared by a phase comparator 22, and constitution of the controlling device is simplified.</p> |
