Patent GB-1451445-A (GB)
Title: Touch plate switch arrangements
IPC: H03K17/96
Filed: 1972-07-31
Abstract: 1451445 Touch responsive switching systems HUGHES MICROELECTRONICS Ltd 30 Oct 1973 [31 July 1972] 35632/72 Heading G1N [Also in Division H3]  A touch responsive switching circuit includes a bi-stable control circuit which when the switching circuit is actuated, is set to provide an output to an external circuit to be driven and a latching circuit responsive to the output and arranged to hold the control circuit in its set condition. A channel selector for a T.V. receiver includes a plurality of circuit elements Aa, Ab & c.Fig. 1, one for each channel and each element A being connected to a tapping point on a resistor chain R 3 , R 4 , R 5  which includes a touch responsive switch 1. When switch 1 of circuit Aa is touched the resulting voltage pulse across R 5  gates MOSFET 3 and a voltage pulse across R6 is applied to one input of OR gate 6, the other input of which is zero. Gate 6 thus provides a '1' output which is fed to one input of AND gate 7 and also after inversion at 8 to respective inputs e.g. 13, 14, 15 of the AND gates of the remaining channels Ab, A c  &c. to disable the gates 7 of these channels. When the gates of channels Ab, A c  &c. are disabled '1' inputs are applied to 13, 14, 15 of gate 7 with the result that AND gate 7 provides a '1' output. At the end of the voltage pulse from across resistor R 6  OR gate 6 maintains its '1' ouptut due to the presence of a '1' from the output of gate 7 and circuit Aa remains in its actuated condition with all the remaining channels unactuated. The '1' output from gate 7 is also used to switch on transistor 4 to cause neon light 2 to be on and transistor 3 to be driven to its on state to hold the bi-stable circuit 6, 7 in its set state. Transistor 5 is also switched on which causes voltage sensitive capacitor 10 to switch on, the latter forming part of the pre-set, by resistor R 8 , tuning circuit of the T.V. channel corresponding to circuit Aa. The arrangement could be used to tune a radio receiver. In an alternate arrangement Fig. 2 and Fig. 3 (not shown) a channel selector includes six channels each as shown in Fig. 2 with each channel being associated via line 11a with a respective resistor chain including a touch responsive switch, a neon indicator and via line 19a with variable capacitor diode of a turning circuit. When a respective touch switch is touched MOSFET 3 is gated on which gates MOSFET 20 on which provides a signal via transistor 16 to gate transistor 21 on. This latter transistor causes bi-stable circuit 22, 23 to assume its set condition which thus supplies an enabling signal to transistors 4, 5. Transistor 4 when enabled supplies a voltage from C to MOSFET 3 to consolidate the bi-stable circuit 22, 23 in its set condition and light the respective neon. Transistor 5 permits a tuning voltage to be applied to the respective tuning circuit. Transistor 24 of each channel is connected to the bi-stable circuit of each of the other channels so that if one of the other channels assumes a set condition it charges its own bi-stable circuit to the reset condition so disabling transistors 4, 5. Remote control. A negative going voltage derived from a remote push button switch triggers a generator to supply signals of phase # 1  to transistors 16, 17 and of phase # 2  to transistor 18. Transistor 21 in each channel is thereby rendered responsive to the condition of the bi-stable circuit of the preceding channel. If the preceding circuit is in its set condition a signal indicative of this is fed via transistor 18 to transistor 21 to cause its respective bi-stable circuit to assume its set condition and its channel to be selected and the preceding channel to be switched off. In this way all the channels may be selected in turn to enable the programmes to be observed before making the required selection.