You flip a switch on and nothing happens. Is the problem the light fixture or the wall switch? Today, you'll learn how to tell if a wire is "hot" and if something's working or not. It's done with a nifty little electrical testing device called a voltage detector or volt sniffer. It's so called because it detects or sniffs voltage by picking up on the magnetic fields surrounding or passing through live electrical wires, switches and fixtures. Its benefit? It removes any mystery whether there is power within, without making direct contact to test it and, thus, eliminates any shocking surprises. While it is generally regarded as a professional tool, it's an affordable safeguard for the home handyman too -- with a basic model costing only about $50. It's a tool or gift for those who are electronically challenged, safety-minded or gadget gurus. You'll find voltage detectors at most electrical contractor supply houses. And that's the On The House tip for today.