This is the famous light dimmer of "Close Encounters" fame !
I needed a mains light dimmer that functioned with pushbuttons rather than the usual rotary knob. It was to equip our guest bedroom (decorated, at last) with control buttons next to the two beds and next to the door. I didn't want to spend more than around 30€, but the ones I found in the DIY shops were over 50€. So, do some design work !
The design brief was to create a cheap light dimmer that could be controlled by three (or more) standard mains pushbutton wall switches.
The basic idea is this :
