This protective circuit for power lines was found in a Radio Electronics from November 1957. The transistor used can be any general-purpose transistor such as the CK722.
This circuit can be interleaved between guitars and guitars to give the fuzz distortion effect. The...
This 1969 Philips documentation circuit makes it possible to control an engine through the sound...
This circuit, suitable for tube equipment, was found in an old documentation. It uses a high...