Forget speech-recognition software: How about typing a letter just by thinking it?

In a quiet corner of the Cebit trade show a small Austrian company is showing a "brain-computer interface," a technology that could one day transform how we use computers, play video games and even talk to each other.

It sounds like science fiction but is a clever application of science and technology. The system does not really read thoughts; rather, it measures fluctuations in electrical voltage in the brain and translates them into commands on a computer screen.

The system consists of a cap that fits over the user's head, with a few dozen holes through which electrodes are attached so they rest on the scalp. The electrodes are connected via thin cables to a "biosignal amplifier," which transmits the signals from the brain to a computer.

Different parts of the brain are used to process different types of thoughts. Vertical and horizontal hand movements are handled in an area called the sensory motor cortex, for example, said Christoph Guger, CEO of g.tec, which built the BCI system shown at Cebit.

To use a BCI to move a computer cursor, the electrodes are placed over the corresponding part of the brain, where they read tiny fluctuations in voltage and feed them into a software program that analyzes them to figure out what the person is thinking.

The software needs to be trained to read the signals, which takes several hours to do properly. The subject responds to commands on a computer screen, thinking "left" and "right" when they are instructed to do so, for example. Another test involves looking at a series of blinking letters, and thinking of a letter when it appears.

The software "learns" what the brain's voltage fluctuations look like when those directions or letters are thought of, Guger said.

The system today is also quite slow -- even a trained system can "read" only 18 characters per minute, or three or four words. Still, that may be helpful for a disabled person who cannot communicate through speech or movement. About 200 disabled people worldwide are using the software at home to communicate, according to Guger, although they need professional help to set it up.

Another issue is accuracy. In a test at a conference in Austria about two years ago, 300 attendees were trained on the system for 30 minutes. After that time the system could figure out simple binary responses from most of the people 60 percent of the time -- or "better than random," Guger said. For 7 percent of the people, the accuracy was more than 90 percent, he said.

The technology is advancing. Five years ago the system was too bulky to be transported easily, and now the various parts can fit in a shoebox. In 10 years it could be fast and accurate enough to commercialize in home PCs or games consoles, according to Guber.

"Ultimately you could have wireless contacts embedded in the brain, and communicate with others just by thinking," he said. "But then you really would have to worry about your wife finding out about your girlfriend."

At Cebit, a colleague of Guber's donned the BCI system and played the game "Pong" against a reporter. It has also been used to write letters, operate artificial limbs and steer a wheelchair. "It's not safe enough for wheelchairs today though; if it reads a command wrongly you could veer off into the road," Guger said.

The study of BCI took off in the 1990s, primarily at three laboratories, in Austria, Germany and the U.S. There are now 300 laboratories working on it, Guger said. He completed his Ph.D. in BCI at the Graz University of Technology, in Austria, in 1999, he said.

He sells his BCI systems mainly to scientists for research work. They are priced from Euro 20,000 (US$26,000) to Euro 100,000 depending on their sophistication. The company is showing a smaller, Pocket PC-based device at Cebit that starts at Euro 3,000. More information is at g.tec's Web site.

Measuring the brain's electrical activity like this is called electroencephalography, or EEG. It is noninvasive, meaning the electrodes are placed on the scalp without surgery, but it produces weaker signals and is subject to noise interference.

Invasive techniques produce better results but are tried only on patients who require brain surgery in any case, and on monkeys and other animals.

An engineer in the U.S. holds a patent on the general BCI concept, Guger said; other patents are held by universities for specific software algorithms used to decode the brain's signals.

G.tec's BCI is among the nominees for the European ICT Prize, the winners of which will be announced Friday. There are three grand prizes of Euro 200,000 each.