GB613857A - Improvements in or relating to television transmitters and receivers or the like - Google Patents

Abstract

613,857. Television. WHITE, E. L. C. Jan. 26, 1946, Nos. 2614 and 23790. [Class 40 (iii)] [Also in Group XL (c)] In a television system in which sound signals are transmitted by modulating the line synchronizing pulses, it is arranged that an interval always occurs between a line synchronizing pulse and a frame synchronizing pulse. In one embodiment the picture signals 1, Fig. 1, are interspersed with line and frame synchronizing pulses 2, 3 respectively, the duration of the former being modulated by sound signals, their leading edges remaining fixed and intervals 24 are arranged to occur between pulses 2 and 3 when line synchronizing pulses occur during the frame retrace period. When a system of interlaced scanning is used wherein alternate frame synchronizing pulses only are preceded by line synchronizing pulses, dummy pulses may be transmitted during the vacant intervals. At the receiver a valve 12, Fig. 3, selects the sound modulated pulses, being supplied with received signals through condenser 10 and with a gating pulse waveform 17, Fig. 2, from the cathode-ray tube line scanning coil 9 through circuit 13, 14, 15 by which limited pulses 18 are produced due to flow of grid current and anode bend cut-off. In a second embodiment, the line-synchronizing pulses are of constant duration and comprise a frequency modulated sub-carrier of constant amplitude, Figs. 4, 5 and 7 (not shown). Specifications 455,375 and 458,585, [both in Group XL], are referred to.