A 13-year-old schoolboy in Britain claims to have invented a doorbell which tricks burglars into believing that someone is home at an empty property.

According to Laurence Rook, 'Smart Bell' dials the homeowner's mobile phone when pressed, allowing them to talk to whoever is outside their front door; the device produces a small amount of white noise to give any unexpected guest the impression they are speaking to someone inside the house.

The invention, which uses an inbuilt SIM card and existing mobile-phone technology, would also allow homeowners to give instructions to drivers making deliveries at their property, says its inventor.

Laurence has already sold 20,000 units to telecoms giant Commtel Innovate and is finalising a deal with a second company for a further 25,000 units. When the deal is signed, he will be 250,000 pounds richer, the 'Daily Mail' reported.

"At first I designed the idea because my mum was fed up going to the Post Office to collect deliveries made when we were not at home. When I started to develop the Smart Bell, I realised it could also be a great burglar-deterrent.

"Most opportunist burglars ring the doorbell first to see if anyone is at home, but Smart Bell has the perfect way to counteract this. If you are out and a burglar comes up to your door and rings the doorbell, after ten seconds Smart Bell will ring through to your mobile and you'll be able to answer.

"There is a small amount of white noise so it will sound like an intercom and the burglar will never know that you're not actually inside the house," the teenager from Surrey was quoted as saying.