Decrease in - and amplitudes measuring system for synchronizing signals in television converters, in particular for satellites of a lead via supporting

摘要

A television sync extraction circuit 3 includes a comparator 21 having a reference level R varying with the amplitude of the sync signal obtained from an amplitude measurement circuit 2. The circuit 2 has a pair of samplers 6, 7 for sampling sync and blanking levels under control of the sync signal extracted from the extraction circuit 3 and a differential amplifier 12 for providing the amplitude of the sync signal as the difference between the sampled levels. The sampler control pulses are generated by monostable vibrators 25, 26 which respond respectively to the rising and falling edges of a pulse generated by a timer 24 in response to a frame sync pulse (SQ, Fig 2). The sync extraction circuit operates at low S/N ratios and also in the presence of 'sound-in-sync'. IMAGE