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 frequency band below 15 kHz converter was found in a Popular Electronics from the 90's. The...
The circuit presented is a 10 MHz oscillator with crystal, which already has several splitters for...
We found this circuit in the November 1992 issue of Radio Electronics magazine. The circuit has...