Found in a 1924 book by Gernsback, this circuit uses a double variable capacitor, a component not very common at the time. Listening was done on a loudspeaker at the time.
This is a typical source of the time (1989) using the well-known regulator integrated circuit 723....
Found in American documentation from 1964, this circuit uses transistors from that time, which are not...
In the circuit of the figure, we have an application different from 4093. The astable...