This circuit was found in documentation for radio amateurs of the 1980s. The circuit is intended to produce a tone for modulation in telegraphic transmissions.
In the figure we have a sensor circuit that makes use of common transistors and a photo diode as...
This unusual configuration, but which has already been explored in other articles, uses diodes in the...
This circuit uses a modulated signal from a PLL 567 to operate safely with an infrared emitter. The...