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.
A touch in this circuit turns-on the lamp or the relay. Power supply is according the lamp or...
Found in a Popular Electronics from the 90's, this circuit uses integrated from that time, today...
This isolated shield for triac was found in old European documentation. The resistor R1, in fact,...