This circuit is from a 1980's documentation for telecommunications. The circuit is used in SSB and the diodes must be suitable types for the application. The audio input is low impedance.
This circuit was obtained from an English magazine from 1976. What this circuit does is start from...
A modulated (flashing) siren using the four gates of the 4001 integrated is shown in the figure....
We found this load control circuit on the power grid using a SCR and PUT in a thyristor manual...