This charger for automotive use provides a 0.42 A output current. We find it in an American documentation from the 90's. The transistor must have a heat sink.
The purpose of this circuit is to allow common analog multimeters to measure low resistances, on...
We found this circuit in a Radio Electronics issue from July 1969. The lamp remains on until C1...
This circuit was found in a 90s Popular Electronics. The sensor can be any phototransistor. ...