This is the commercial circuit for the TRF-44 amplifier sold in Japan in the 1960s. The circuit provides a few hundred milliwatts and is intended to be used as small, battery-powered turntables.
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...