In this circuit the LED lights up when the voltage drops below the value set in the trimpot. The transistors can be the BC548. The circuit is from a 1999 American publication.
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...