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.
In this circuit, from a documentation from the 70's, we have the way to control the active cycle of...
This circuit was found in Popular Electronics from 1969. The circuit uses a small speaker as a...
This circuit can function as a circuit breaker or current switch opening with a current according to...