This circuit is from a Radio Craft from the 1940's. The circuit employs 5 tubes and must be battery powered. See that the circuit is quite critical, especially in relation to the sensor coil.
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...