This circuit was obtained in a 1967 Raytheon manual. The company's component is an optical coupler with a photo-resistor and a lamp. Transistors support equivalents.
This circuit is from an old technical documentation from Spain. The circuit uses a FET that is...
Found in a documentation from the 90's, this circuit already includes an amplification stage. The...
This circuit, called Kames Dandy, can mix signals from a wide range of frequencies and is...