Fancy building your own Klingon Disruptor? An ex-US Navy engineer has done just that for the bargain price of $500. The gadget fiend has built a 'gun', using readily available hardware that can disable almost any piece of electronic equipment from 20 feet away.

It consists of a parabolic reflector, a horn antenna and two ignition coils and is powered by a car battery. When the inventor, David Schriner demonstrated his new toy at the Infowar 99 conference in Washington DC, it disrupted the PA system and two nearby PCs, which needed to be reset even after the 'gun' was switched off.

The principle it exploits dates back to Tesla. In essence, the gun shoves a 20 megawatt burst of radio noise through the antenna, which then interferes with nearby electrical equipment, according to US newswire reports.

Schriner said the demonstration was intended as a wake up call to the electronics industry. He said he wanted to show that even low-budget saboteurs could inflict serious damage. He claims to have built another machine capable of crashing computers, and cars from a distance of 100 feet. That one cost him less than $300.

Permanent damage is rare, Schriner says, but that is not the point. The computers at the conference worked after re-booting. "But if that happens to be a computer in a tank, or in a piece of medical equipment, how long does it take to reboot?" he asks. "By that time you could be dead." ®