To do that, the system essentially bombards the space with an array of wireless signals and keeps watch on any changes in signal strength, building up a "picture" of the room in the process.

ENGADGET: Researchers create Amazing X-Ray Wireless Network!

The prototype white-space devices used in trials had little trouble sensing occupied TV channels, typically picking them up at signal strengths less than a thousandth of that needed to display an image on a TV screen.

ECONOMIST: Difference Engine