This space mark demodulator for FSK signals was found in an American telecommunication documentation from the 1980s. The circuit operates with 2025 Hz and 225 Hz mark space signals.
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...
We found this circuit in a Radio Electronics from January 1967. The SCR is already the C106, which...
This power source with silicon diodes at a time when valves were still used was found in Radio...