I have seen home made versions of this before.
Roadies or stage hands what ever you want call them use a home made version.
Usually 2 NEMA 5-15 male cord caps running into a 30 amp 3 wire dryer outlet or a 50 amp 3 wire range outlet.
This will power a dimmer rack and the roadie just does not crank up all dimmer banks at once.
I have seen DJs, and small rock shows use this method.
If you open the box I imagine the only "electronics" will be for the indicating LEDs.
