This primitive solar radio was found in a Gernsback publication from 1960. The transistor is made of germanium of the time and the earphone is magnetic with high impedance.
This amplifier with the RCA CA3018 integrated circuit was found in the August 1970 issue of Radio...
This circuit generates sinusoidal signals that depend on the input oscillator. The circuit is from...
This fast-acting circuit uses any phototransistor as a sensor. The circuit drives a 30 V relay, but...