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 is an excellent shield for microcontrollers and was found in the October 1987 Radio...
This power supply can supply voltages of 6, 9 or 12 V depending on the zener used. The maximum...
The integrated circuit used is no longer very common today, but there are still many sources that...