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.
The critical components of this 1978 circuit are transformers, which, hopefully, can be obtained from...
This circuit was found in a 1995 documentation, consisting of a car protection system that blocks...
Suitable for dual applications, this timer was found in a 90s Popular Electronics. The circuit...