GB606314A - Improvements in or relating to signal pulse selection circuits - Google Patents

Abstract

606,314. Television receivers. SADIRCARPENTIER. Jan. 15, 1946, No. 1413. Convention date, March 20, 1945. [Class 40 (iii)] [Also in Group XL (c)] Pulses are selected from trains of impulses comprising pilot and secondary pulses, by applying said trains to a delay line, whereby interference occurs between outgoing pilot pulses and reflected secondary pulses, the desired pulses being selected at pre-determined points in the line by circuits with appropriate threshold biasses, which may comprise optical elements for reconstituting a television image. In one embodiment, the amplitude of the pilot pulses is at least double that of any of the intervening amplitude modulated pulses of a multi-channel communication system and the channel pulses are separated by applying the received pulse train to the input terminals 6, 7 of a delay line 1 ... 5. The channel circuits 16 are connected to intermediate points 11 ... 15 on the line and biassed by voltage source 18 so that they respond only to pulses greater in amplitude than the pilot pulses and produced by the summation of an oncoming pilot pulse and a secondary channel pulse which has been reflected from the open-circuited end 9, 10 of the line. The input end of the line is shunted by a resistance 8 equal to the surge impedance of the line. In a second embodiment, the terminals 9, 10 of the line are shortcircuited and the pilot pulses are then arranged to be of opposite polarity to the secondary pulses so that the latter, on reflection and change of sense, are additive with respect to the pilot pulses. For television reception the circuits 16 may be constituted by electrooptical elements, for example neon tubes, the source 18 providing a voltage just below their ignition voltage so that the degree of illumination is a function of the amplitudes of the secondary pulses.