We found this circuit in a 1967 documentation. The integrated circuit and an operational one of the time. Modern equivalents can be tried out. The power supply is symmetrical.
The presence of a low resistance between the terminals of the sensor causes this modulated...
TDK provides a wide range of EPCOS varistors for surge protection through Mouser Electronics....
This circuit was taken from a Popular Electronics from January 1967. Transistors are from the...