GB673972A - Improvements in or relating to circuit arrangements for converting pulses of differen durations into pulses of different amplitudes - Google Patents

Abstract

673,972. Television. ELECTRIC & MUSICAL INDUSTRIES, Ltd. June 5, 1950 [June 4, 1949], No. 15062/49. Class 40 (iii). [Also in Group XL (c)] In a pulse width discriminating circuit pulses of different durations are converted into pulses of different amplitudes by applying them as current pulses to an open-circuited delay network which has a time delay which is greater than half the duration of the narrower pulses and less than half the duration of the wider pulses so that the pulses applied to the input of the network are reflected at the open-circuited end to produce wider pulses at the input with enhanced amplitude which may be separated by an amplitude filter. The Figure shows a pulse discriminating circuit for separating frame synchronizing pulses from the combined line and frame synchronizing pulses in a television receiver. The incoming pulses are applied at terminals 3 to the grid circuit of a valve 4 in whose cathode circuit is a delay network 5 which is short-circuited at end 7. Cathode resistor 6 enables the network to be matched by its characteristic impedance at the input end. The delay of the line is such that only the wider frame synchronizing current pulses after reflection at end 7 overlap and appear at enhanced amplitude, Fig. 1 (not shown), across the input end of the network 5 and also across the anode load resistor 8, where they may be separated by an amplitude filter. Specifications 420,391, 455,373 and 491,728 are referred to.