This circuit comes from a Gernsback Publications of the 90s. The circuit uses a general-purpose transistor as a sensor. The power supply must be symmetrical.
This experimental telegraphic communication system can have wires connecting to the handset of...
Scratch is the scratching noise that occurs mainly with old records. This high frequency noise is...
This short-range circuit can act as a wireless microphone. We got the schematic and the printed...