Found in an English publication from the 1980s, this circuit can be built with equivalent transistors such as the BC549. The signal must be applied to an external amplifier.
This circuit works with small 5 V incandescent lamps but can be modified to operate with LEDs. The...
This circuit found in Radio Electronics can be used in games to produce a random pulse train. The...
This photometer is based on a Wheatstone bridge that must be balanced by the linear potentiometer P1. The...