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.
We found this circuit in the March 1992 issue of Radio Electronics magazine. The circuit has a...
The circuit presented may use any general purpose transistor. The indicator is an LED and...
This unusual audio amplifier configuration was obtained in a 1974 documentation. The PNP...