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.
This circuit was found in an English magazine from 1979. The magazine no longer exists, but the...
This 2001 CMOS digital circuit draws numbers from 00 to 99 and can be expanded. However, it does...
The sensor in this circuit is a BA315 diode. Other diodes can be experimented, but this is one...