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 circuit was found in the September 1984 issue of Radio Electronics magazine. The frequency is given...
We found this circuit in an Argentine documentation from 1973. The transistor admits a more modern...
This triac synchronized circuit was found in the July 1995 issue of Electronics Now magazine. The...