This circuit is from a Radio Electronics from February 1966. The circuit is of a type that was found in many applications at the time as output from radios, televisions and other equipment.
This circuit uses an MW radio tuned to around 540 kHz to detect atmospheric signals, for example, from...
This project was found in a 1982 publication. It is a small transmitter that can send signals from...
This circuit is from a 1960 book by Hugo Gernsback. The transistors are germanium from the time....