Ever wake up late at night and hear what sounds like a burglar walking around downstairs? It can?t happen if you?ve equipped your home with the new burglar alarm developed by Swedish scientists that will go on sale in England this year.

When the device, known as Inferno, is set off, the sounds it makes are so unbearable they can cause physical nausea. It can be attached to existing burglar alarms and emits low-frequency sounds that grate against each other. In tests, volunteers were able to endure the sounds for a maximum of 80 seconds before running out of the room.

David Midgley, a former policeman who works for the company says, ?It produces the same reaction as someone drawing their fingernails down a blackboard. We have tried it on volunteers and the reaction ranges from symptoms of dizziness and disorientation to a feeling of sickness. I myself have been a guinea pig and the longest I managed was 10 seconds?it is no louder than a standard alarm, but it just makes a horrible noise.?

If you decide you have to go downstairs to investigate, you?ll need to take the right flashlight. Try to get one of the new RADAR flashlights, developed at the Georgia Tech Research Institute, that can detect a human presence through doors and windows up to 8 inches thick.

You hold the flashlight like a gun and pull the trigger to activate it. When held close to a window or wall, the RADAR?s narrow beam sends out a pulse of electromagnetic energy, then detects the return signal, which is read by high-speed signal processing technology that quickly delivers bar-graph results on the user?s display. As the person on the other side of the wall breathes, the bar-graph display rises and falls with a rhythmic response.

?We have one problem,? says Gene Greneker, one of developers. ?This instrument is so sensitive to motion that if you don?t hold it still enough, it will detect its own self-motion.?

There?s another problem too: ?Our target sales price is $1,000 to $1,500 per device.?

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