This code key uses a PLL and an oscillator that generates two frequencies that must be recognized for the relay to be activated. The circuit is from an 80's Popular Electronics.
This circuit can serve as the basis for a small FM transmitter with varicap. We found it in a...
This circuit was obtained from the Radio Electronics magazine of August 1962. It is a tandem...
This 10 A solid state relay was found in a 1980s documentation. It can work as a shield and...