They’re drum sequencers, it’s a really old way of making scrolling light shows for things like signs and stage displays. They used to use (usually less fire hazard-y) versions of this q long time ago in Vegas for the giant hotel signs and things.

I remember seeing a video of a light display in Cuba. They couldn’t get much in the way of controllers so they used a rotating drum of electrical contacts to open and close circuits for animation effects. This looks very similar to that. Pretty ingenious but totally unsafe.

Arcs don’t need to be high current. But this will absolutely fail at some point, how soon is a question.