This traditional dimmer configuration for incandescent lamps and heating elements was found in an RCA transistor manual. SCR can be a more modern equivalent like TIC106, depending on the power grid.
The circuit shown in the figure below is suggested by ON Semiconductor (www.onsemi.com), based on...
This control is intended for 110 VAC or 220 VAC Motors. Any TIC series triac can be used according the power...
This circuit was found in a 1999 English magazine, but can be easily assembled with BC548...