| 摘要 |
An electronic unit is used to provide phase-lock-loop tuning in radio and television receivers. It produces local oscillator signals from a reference frequency derived from a cristal oscillator. It has greater reliability and flexibility than the usual passive units. The unit has a series of preset resistors, a mono-stable multivibrator, and a programme selector to select the duration of the programming. There are also a local oscillator, counters, a switch and a phase comparator. The comparator produces an error signal representing the deviations in phase and frequency between the reference frequency signal and an output signal, nad also produces a signal for adjusting the local oscillator. |
