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.
The integrator in the figure is characterized by low input current and is based on an LM101A. C1...
This circuit was found in an ancient American documentation. The integrated circuit is of the time...
This circuit, from a 1976 documentation, amplifies signals from 100 Hz to 600 kHz with a voltage fan...