| 摘要 |
<p>A magnetic disc video recorder has a phase locked servo loop control for the disc drive. If an incoming signal is present, the horizontal sync information is separated from it and used to key a free running oscillator which in turn provides a reference signal to the servo loop. When no equalizing pulses are present in the incoming signal, the oscillator rings through the vertical interval. If there is no incoming signal, the oscillator is automatically converted to a crystal controlled oscillator.</p> |
