This 50 Hz rejector or notch filter was found in a 1975 documentation. Other frequencies can be obtained by changing components. The filter uses a Wien network and must use a symmetrical power supply.
This spinner (see CB18894E) uses only an operational amplifier that must be powered by a...
The incidence of light in the LDR causes this circuit to start operating, emitting a sound whose...
This circuit is from American documentation. The components used are still common. The power...