GB1444923A - Receiver for use in the control of apparatus by digital signals - Google Patents

Abstract

1444923 Command signal receiver INTERNATIONAL STANDARD ELECTRIC CORP 24 Aug 1973 [1 Sept 1972] 40251/73 Addition to 1429681 Heading G4H [Also in Division H3] The invention relates to on/off mains switching of apparatus controlled by digital signals and is for use in the system of Specification 1,429,681. As shown, a TV receiver 51 is connected to a mains supply by contacts 50 of a master switch and by the contacts 49 of a relay 48 which receives remote control commands as in the above mentioned Specification. The following conditions are to be satisfied: (1) The master switch controls on/off switching independently of relay 48; and (2) With contacts 50 closed, the TV remains off on restoration of the mains supply after a failure. With contacts 50 open, and irrespective of the position of contacts 49, rectified mains current via R6, C7, C8 causes a transistor T8 to conduct, thereby applying battery voltage U2 to a resistor R5, whereupon a transistor T7 is rendered non-conducting. If, in addition, relay 48 and transistor T6 are not supplied with current, then C6 charges to the voltage of the junction of resistors R3, R4 derived from a potential U1. If contacts 50 are now closed, the voltage available to C8 is reduced, T8 is switched off and T7 conducts. T7 discharges C6 via D3 to the input of flip-flop 47, causing relay 48 to respond : operation of the relay closes contacts 49 to apply mains voltage to the TV. On further actuation of the master switch, contacts 50 open but contacts 49 remain closed: the TV is switched off, but relay 48 remains energized since U1, U2 are unaffected. T8 starts to conduct again, connecting U2 to R5 and switching off T7. When contacts 50 close again, contacts 49 being already closed, the TV immediately receives the mains voltage (there is no switching pulse for 47 since C6 has not had time to charge via R3, which is of very high value). If a mains failure removes U1, U2, then flip-flop 47 loses its 1-level output, which remains at 0 upon return of the supply voltage, relay 48 remaining de-energized (the charge on C6 is conducted away via T7).