This circuit is from an old American documentation from the 70s. Transistor 2N3904 can be replaced by BC548. The relay must have 100 mA of maximum current.
We find this circuit in documentation from the 1980s. The triac and diac are of conventional types...
We found this circuit in the November 1995 Electronics Now magazine. The circuit is more accurate than...
The filter shown in the figure, suggested by National Semiconductor, only allows frequencies above...