This circuit is from a Texas Instruments manual from 1968 but can be applied to current controls using modern Triacs. The circuit is for a current of 25 A per triac.
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...