TAP switch

The advantage of this circuit for a touch activated switch is that it requires only one set of contacts and uses only two inverters, two resistors and a pair of capacitors. The circuit functions as follows: At switch on, the input of N 1 is low, since C I is discharged. Since the input of N 1 is low, the input of N2 must be high and the output of N2 low, which of course holds the input of N 1 low -thus the circuit is latched in a stable state.