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 obtained in Linear Technology documentation from 1993. The circuit provides 3.3 V and...
This circuit is from the National Semiconductor CMOS manual of 1977. What this circuit does is to...
This circuit operates from 25 to 65 kHz depending on the transducer used and the settings. We...