| 摘要 |
<p>The lock-on circuit is for automatic tuning systems in television receivers. It consists of an input monostable fed with line flyback pulses and a second monostable with a different dwell time which is fed with a signal derived from an amplitude limiter fed with received signal. The outputs of the monostables are taken to a comparator which, at coincidence, charges a capacitor. If a high noise level is detected by the input filter-limiter, then a second comparator triggers a transistor which discharges the capacitor, thus preventing a stop signal from being sent to the automatic tuning circuit. If a transmitter is identified and a stop signal produced, this resets a bistable to switch the line oscillator back to normal operation.</p> |
