| 摘要 |
In the illustrative embodiment, a one shot multivibrator is adapted to receive an incoming FM signal at its input, and in operation generates a series of pulses which coincide in time with the positive peaks of the received FM signal. The series of pulses generated by the multivibrator is in turn applied to an initiate/reset input of a free-running pulse generator which is arranged so that, when it is permitted to free-run, it emits a train of pulses having a preset pulse interval identical to the interval between successive positive peaks of the incoming FM signal at the particular point in time when the instantaneous voltage level of the modulating signal component of the FM signal is equal to the predetermined voltage level. The application of the pulses from the multivibrator to the initiate/reset input of the pulse generator synchronizes the pulse generator to the multivibrator, so that an output from the pulse generator is an indication that the predetermined voltage level has been crossed by the modulating signal component of the FM signal. The illustrative embodiment also may include a coincidence circuit which in operation compares the timing of the pulses from the multivibrator with the timing of the pulses from the pulse generator and generates an output signal when coincidence occurs, each output from the coincidence circuit serving to indicate a predetermined voltage level crossing.
|
