This sound or voice relay was found in a Popular Electronics. It includes an amplification stage and can be used as a shield.
This simple light meter or photometer circuit uses an analog indicator of 0-1 mA. Power is...
Found in a 90's EDN, this circuit provides a current of a few tens of mA. The circuit can generate 15...
The author of this project found in a 1980 documentation gives the radio in two versions: the...