Found in a 1924 Gernsback publication this circuit uses 4 batteries for power and loop antenna. Listening is over a high-impedance type earphone or loudspeaker common at the time.
Suggested by National Semiconductor in a documentation of the 90s, this circuit uses a power...
This circuit was obtained from an American 1980s documentation. The frequency depends on the...
The sensor of this circuit is a large surface diode. We believe that a small solar cell can also...