This circuit was obtained from the April 1978 Radio Electronics magazine. The other circuit is a PLL of the time. The power supply must be 15 V symmetrical.
We found this circuit in a Radio Electronics from January 1967. The SCR is already the C106, which...
In this circuit the LED lights up when the input voltage exceeds the value set in the trimpot. The circuit...
Found in American documentation from the 90s, this circuit uses a high voltage relay and has no...