GB1306467A - Television systems - Google Patents

Abstract

1306467 Multiplex radio signalling INTERNATIONAL STANDARD ELECTRIC CORP 29 Oct 1970 [5 Nov 1969] 51381/70 Heading H4L In a television transmission system of the type in which one or more sound signals are transmitted in time division multiplex with the vision signal, the transmitter includes a storage device to store during each frame period samples of the audio signals occurring during that frame period and is arranged to transmit the stored signals between the end of each frame and the start of the next frame. As shown in Fig. 2, two different audio signals are supplied via terminals 3, 4 respectively to storage devices 6, 7 and the associated video signal is supplied to terminal 5. A control signal generator 26 is synchronized by the colour subcarrier signal and provides low and high frequency control signals on terminals 11, 12 respectively. The audio signals are stored under the control of the low frequency signals and read out under the control of the high frequency signals via a distributer 8 to the modulator input of the transmitter. Switches 8, 9, 10 are operated by control circuits synchronized by the line syncsignals so that the two signals are read out during different line periods of the frame flyback period. At the receiver, Fig. 3, the video signals are amplified and supplied to a cathode ray tube 16 and the audio signals tranmitted in the frame flyback period are supplied via switch 25 to a store 17. The signals are stored under the control of a high frequency signal from terminal 12 and read out by a low speed signal from terminal 11 via switch 18 to operate a loudspeaker 24, switches 18 and 25 being operated together so that when switch 25 is closed switch 18 is connected to terminal 12. A counter 19 receives frame sync. pulses via terminal 20 and line sync. pulses via terminal 21. The frame pulses reset the counter 18 to zero which then counts line sync. pulses until a number corresponding to the first audio modulated line period is reached at terminal c and switch 25 is closed. A pulse at terminal d corresponds to the second audio signal and terminals c, f relate to two other audio signals which are used when receiving other transmitters. One of the two audio signals may be the sum signal and the other the difference signal of a stereophonic system or the signals may be in different languages. The storage device may be of the "bucket-brigade" type or magnetic recording may be used.