This circuit uses an unusual sensor nowadays, but the configuration can be adapted to more modern types, as well as the operational amplifier. The circuit is from an 80's documentation.
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...