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 was found in a 1966 General Electric documentation. The circuit makes use of PUTs...
We found this circuit in the April 1979 Radio Electronics magazine. Note the filter capacitor bank...
This transmitter has a good output power thanks to the amplification step with two transistors. The...