Touch-sensitive control circuit

摘要

A touch responsive user selection system including a plurality of touch pads on an insulated substrate and a logic circuit for responding to the change of impedance of any of the pads for setting or resetting a latch and thereby producing an output signal indicative of a user selection. A coincidence detector responds to the simultaneous change of impedance of two or more different touch pads by inhibiting the logic circuit from producing an output signal both during the coincidence and for a predetermined period of time after the coincidence has ceased. The logic circuit is made up of components that are arranged in a fashion that causes the circuit to respond to a ratio of signals that vary in proportion to supply voltage. In this manner, a touch-responsive system is provided that may be used with an unregulated power supply while functioning with extreme variations in supply voltage.