This circuit was found in a 90’s EDN. The components used are still common and the sensors can have their quantity increased. The supply voltage is according to the relay.
The circuit shown in the figure was found in a 1974 publication. The field effect transistor may...
I found this circuit in an English publication from 1989. This configuration can be mounted with...
We found this circuit in a small espionage manual from 1993. The components are current, and the...