This is a sweet sounding, oldskool incandescent bulb driven vibe/optical tremelo.
The great Madbean's Qudrovibe. Visit Madbean Pedals if you'd like to build your own, or contact me, I think I've a couple of spare boards squirreled away somewhere.
An internal voltage doubler supplies 18v for increased headroom and to run the lamp, the same as in a vintage Uni-Vibe.
The switch toggles between the vibrato or sweet optical tremelo. The volume control provides considerable boost, a gentle compression and adds some sparkle.