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 photoelectric circuit from a 1960 publication uses a 6.3 V electromechanical counter, common at...
We found this circuit in a magazine 73 from the 90's. It is a circuit indicated for radio-amateur...
) This circuit uses two 4046 CMOS PLLs to produce a modulated signal of good intensity. The MOSFET can...