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 was found in 1980s Electronic Engineering. Transistors can be modern equivalents. The...
We found this circuit in the February 1970 Radio Electronics magazine. It can be used in an analog...
The sensor in this circuit is an LDR and the potentiometer serves to control the sensitivity...