This circuit is from the 1989 special edition of Radio Electronics Experimenter. The circuit was created with SMD components to be mounted on a keychain.
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. ...