Published in an old Popular Electronics, this circuit makes use of components that are still current. The circuit must be powered with 9 V and eventually adapted to function as a shield.
This circuit was suggested by Motorola in a 1980s publication. It is based on a PUT that is not a...
We found this circuit in an old documentation, using an operational of the time. The circuit...
This circuit uses a pickup coil to take the signal from a telephone line without contacts. The circuit...