GB1352038A - Television receiver - Google Patents

Abstract

1352038 Television; multiplex radio signalling MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 19 April 1971 [8 April 1970 (2)] 26133/71 Headings H4F and H4L A television receiver receives a video signal comprising two sets of video signals transmitted in a line sequential manner and an audio signal on a carrier, the audio signal comprising one audio signal and a second audio signal on a subcarrier, the audio signals being reproduced at loud-speakers 11, 13, Fig. 1, respectively. The video signal is fed from a detector 3 to a switching circuit 22 where the sets of video signals are separated, one set of signals being fed to output circuit 18 and the other to output circuit 19. Each output circuit 18, 19 has associated with it a one-line delay line 20, 21 so that each line of received information is displayed on two adjacent lines on the respective cathoderay tube 14, 15. The switching circuit 22 comprises a bi-stable multivibrator 44, Fig. 2, operated by the horizontal synchronizing pulses from a synchronization separator 5 via transistors 34, 40. The output of multivibrator 44 is fed via phase-splitting transistor 48 to alternately switch on and off transistors 56 and 64 which feed the signals from detector 3 to the output circuits 18 and 19. During the vertical blanking period the vertical synchronizing signals from separator 5 are integrated by resistor 69 and capacitor 70. When the integrated signal reaches a predetermined value transistor 81 is cut off and the collector voltage of transistor 81 rises, and triggers a monostable multivibrator 86. The output from the multivibrator 86 is passed to a multivibrator circuit 88 which includes a transistor which is cut off by this output, so cutting off the power supply to multivibrator 44 for a predetermined period. The output from the multivibrator 86 also cuts off transistor 40 for a longer period, so that the output of multivibrator 44 is zero during part of the vertical blanking period, the transistor 56 being biased on and transistor 64 off. The first horizontal synchronizing pulse from separator 5 after the pulse from multivibrator 86 finishes thus causes transistor 64 to be turned on and transistor 56 off, so that during every frame the correct set of signals is supplied to the correct output circuit 18 or 19, as the first line of each frame is a line of a specified one of the two sets of video signals.