A blind man, arriving in a large city for the first time, climbs off the train and strides briskly out of the station. He turns purposefully left and then right, walks for another 100 yards, crosses a road - negotiating parked cars, a lamp post and a tree - and goes straight into a shop. He has travelled alone, with- out even a guide dog to help him. So how has he done it? The answer lies several miles overhead: he is using computerised satellite signals to plot a detailed map for himself.
Known as MoBIC (Mobility of Blind and elderly people Interacting with Computers) the communications system is poised to go on the market in Germany and could be available in other European countries by the summer.
Such extra-terrestrial guidance - adapted from the global positioning systems (GPS) employed by the US and Russian military to send missiles to their targets - is already being used in sea and road navigation devices.
The prototype for visually impaired people comprises an indoor planning system and an outdoor satellite receiver. Its backpack weighs around five kilograms. To use it, you key your address and your destination into a small talk-back computer which works out the swiftest route, using electronic Ordnance Survey maps.
Having chosen your route, you don the backpack and earphones and head out of the door. Lose your nerve and you can check your progress with a wrist-operated keypad. Take a wrong turning and the voice in your ear will alert you be- fore you are lost.
The EU-funded project follows several years' collaboration between a consortium involving universities in Birmingham and Hatfield, the Royal National Institute for the Blind, British Telecom and experts in Sweden and Germany.
Juergen Bornschein, product developer at FH Papenmeier, in Schwerte, Germany, which is marketing the device, hopes a planning software package costing around £300 sterling will be in the shops by July or August. This, he says, would allow users to plot routes in an area the size of a small town. But he stresses: "This does not include the cost of the computer - just the software and the electronic area. We anticipate the outer system, which is much more expensive and involves complicated satellite technology, costing around £3,500."
Paul Hopkins (30), business centre manager at the Queen Alexandra College for blind people in Harborne, Birmingham, was one of a dozen volunteers who took part in a six-month trial of MoBIC. He found the system of great benefit.
"It has the potential to give me a lot more independence," he says. "It means I can go to an unfamiliar place and I don't have to ask people to come with me all the time. It's a bit like having your own personal guide with you - very human and friendly. It will provide you with detailed instructions and tell you if there are obstacles such as trees, moving pavements, bus stops.
"Once I got used to it, it gave me a personal freedom I don't usually have. And it was confidence-building, although it took a lot of concentration to master it." Hopkins believes the MoBIC could broaden the horizons of thousands of blind and elderly people every year. "It would be fairly easy to work out a route involving various methods of transport, such as buses and trains," he says. "You would just switch off the device while you were on the train and programme it again for the other end." However, he points to the high cost of MoBIC for anyone who travels regularly outside their home area. "I'm not going to buy something which is expensive or underdeveloped. I would pay £1,000 for one. But I'm sure the manufacturers realise that it has to be affordable - and then the potential is enormous."
The researchers dismiss suggestions that such innovations could spell the demise of essential aids such as guide dogs.