Suggested by a 90’s Radio Electronics, this circuit automatically activates the recording switch of an old tape recorder. It can be adapted for other purposes.
The transistor can be the BD135 and this circuit, found in a 1978 publication, can be powered by...
This interesting circuit measures the distortion of the sinusoidal voltage of the power grid. We...
This sophisticated circuit is from a 1975 documentation. The components are from the time and the...