This circuit is from an ancient American documentation. The integrated circuit is 741 and the power supply must be symmetrical. The passing band is centered at 1 kHz.
Found in a European magazine from the 90s, this circuit emits beeps that are several seconds apart to...
We found this circuit in an American 1980s documentation. The circuit uses a piezoelectric transducer...
Originally suggested by Popular Electronics to control Christmas lights, this circuit can...