This audio oscillator is from a 1957 Raytheon publication. The tone generated depends on C2 and C2 and the handset must be high-impedance magnetic. Equivalent transistors can be tested.
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...