This telephone recording circuit was found in the June 1979 issue of Radio Electronics magazine. The components are common at the time and the power is supplied by the power grid.
This powerful source was obtained in an American documentation of the 80s. Some components are...
This simple transistor tester was found in a Japanese magazine in 1967. It tests general purpose...
This transistorized astable for LEDs was found in the January 1992 issue of Radio Electronics...