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.
We found this configuration in an early 1977 publication. The PNP transistor may be the BC558 and...
This circuit is indicated to operation with piezoeletric transdicers or other with high impedance...
This circuit was found in a 90s Radio Electronics. The load is an LED, but the circuit can be...