The capacitor used in this circuit can have values between 5 and 30 uF. The circuit is of old documentation for radio amateurs. Observe the special source used in the supply.
We find this microphone voice effect in 1992 documentation. The vibration of the relay contacts...
In this oscillator circuit using 3 TTL inverters we have all the conditions for the frequency...
This configuration, explored in other applications of this section and website, was found in a 90s...