GB1439167A - Remote control system - Google Patents

Abstract

1439167 Selective signalling MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 13 Aug 1973 [12 Aug 1972 (2)] 38220/73 Heading G4H [Also in Division H3] A remote control system, more particularly for a television receiver, uses a light control signal which is modulated by a high-frequency signal itself modulated with a low-frequency signal: in the transmitter two transistors are cross-coupled to form a multivibrator which "chops" the high frequency signal generated by one of the transistors, which is back-coupled to form a high-frequency oscillator. Remote control transmitter.-Transistors 1, 2, Fig. 3a are arranged to produce high-frequency oscillations chopped at a low frequency, Fig. 2c (see Divisions H3-H5). A coupling winding 22 drives transistor 24 whose emitter circuit includes the light-emitting diode 25. The arrangement is energized by closing switch 18A; if switch 18B is closed instead, switch 21 closes with it and introduces capacitors 20A, 20B and so changes the transmitted high frequency to provide a different control function. Remote control receiver.-The modulated light signals are picked up by a photo-transistor 26, Fig. 4a, the output of which is amplified by amplifier 28 and following transistor 29. The two transmitting high frequencies are separated by tuned circuits 30, 31 each of which is followed by a detector circuit 32, 33 respectively. Each detector circuit, e.g. 32, feeds into a differentiating circuit 34, 35 the output of which is amplified by transistor 36 and applied to a clamp circuit comprising diode 38. The signal passed by diode 39 is integrated by capacitor 40 and after a preselected time interval renders transistor 41 conductive to operate relay 42.