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 converts pulse frequency to current, which is indicated on an analog instrument. The...
Based on an LM317T, this circuit found in Popular Electronics works with signals of frequencies up to...
The Texas Instruments LM5178 Buck-boost controller is capable of operating in the 4.2 to 55 V (60...