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 that converts very low currents into voltage was obtained in the 80's used component...
This circuit uses a photo-transistor to trigger a circuit sourcing a square signal for the output. The...
This 3-transistor timer was found in the January 1994 issue of Electronics Now magazine. The...