This circuit is part of an oscilloscope project with the PC. Its purpose is to record a peak in a signal that is to be displayed. We found it in the Radio Electronics magazine of February 1990.
This filter that rejects determines frequency (notch) was found in a Popular Electronics of 1993....
Found in an Elektor from the 90's, this double door-bell drive circuit switches a relay by...
Using a 555 this circuit was found in old documentation, but it is still valid. | Clique na imagem...