This powerful transmitter for the 27 MHz band was found in a Japanese publication from 1961. The circuit is powered by battery and has the details of the coils given next to the diagram.
This simple amplifier uses a microphone attached to the telephone. The 3-transistor circuit was...
This toy organ was found in Popular Electronics from January 1967. It can be constructed from...
The circuit below was found in the March 1990 issue of Radio Electronics magazine. The circuit...