Ca6415661 A
This is clever, Bob’s vacuum system turns on whenever he uses his wood working machines…

Woodworker Bob Neidorff bought a vacuum to collect the chips and sawdust from his shop equipment, and plumbed it to the vacuum ports on his power tools and to his homemade vacuum hose ports. But then, he had to turn it on and off every time he used a machine. That is, until he built this gadget. A torroidal power transformer and a handful of electronics detects the load current of the machines involved and controls the vacuum automatically. Now whenever the chips are flying, they’re heading for the vac.

Case #98: Bob Solved His Chip Problem – 2/26/2007 – Design News – Link.