This circuit is from an 80's technical newsletter. The circuit can use any general purpose transistor and its power supply can be changed with a resistive divider to use a single 9V battery.
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...