Found on a 1964 CQ this circuit is intended for tone frequency change modulation (FSK) telegraphic transmissions. It operates with signals of 2.975 and 2.125 Hz.
In the diagram we show how to divide the frequency by multiples of 10 using several CMOS...
The integrated circuit used in this application is a double 741 from SGS. The supply must be...
This circuit was found in a 1978 English magazine. It is a configuration that aims to select the...