This common circuit using operational amplifiers was found in the 1993 issue of Radio Electronics Special Projects. The circuit is sandwiched between the pickup and the amplifier input.
Based on the CA3140 IC, this circuit was found in the June 1986 issue of Radio Electronics....
When sensors X1 and X2 stop driving by the dryness of the monitored location, the oscillator...
This circuit works directly connected to the network and special care must be taken with its...