This small tone generator was found in the November 1987 issue of Radio Electronics magazine. The phototransistor is common and controls the sounds generated. The basic frequency is given by C1.
In the figure we have a way of using a solar cell as a source for circuits with tunnel diodes. The solar...
This equalizer was found in the May 1978 issue of Radio Electronics magazine. The component values...
This circuit for high-impedance magnetic headphones was suggested as an experimental amplifier for hearing...