This circuit is from General Electric from the 80s, using a relay with high current contacts (20 A). The transistor admits equivalent, and any phototransistor can be used as a sensor.
The frequency of the signal produced by this oscillator depends on the amount of light falling...
The circuit presented is based on a mechanical tuning fork. The circuit is suggested by National...
This is a well-known RC oscillator configuration using a 741 operational amplifier. The circuit is from...