STUTTGART/MUNICH, Germany There are two golden rules when driving a car: Keep your hands on the wheel and your eyes on the road.

Hands-free mobile telephone kits can therefore do precious little for road safety if they force drivers to peer down at their mobile displays every time they want to make a call.

In recent years, designers at the upper end of the car market have attempted to overcome this problem with multifunctional steering wheels which come equipped with a series of switches capable of operating everything from the stereo to the telephone.

Notwithstanding the success of these wheels, engineers have now come up with a still more ingenious solution, in the form of voice activation.

This technology has the car hanging on the occupants' every word. A simple spoken command is enough to change the radio station, leaving the driver to concentrate on the task in hand.

However, voice-activated systems are as yet fairly rare. For example, in Germany, disregarding suppliers of radios, telephones, navigation systems and even sunroofs, only two firms currently install the new technology.

Mercedes can rightly take the plaudits as the forerunner in this field. According to company headquarters in Stuttgart, the launch of the new S class saw the introduction of linguatronic, a system enabling voice-activated use of the telephone.

Mercedes has since extended the option to almost its whole model range, with prices in the region of 1,000 marks, or approximately $440.

The new C class, unveiled last spring, boasts a more advanced version of linguatronic capable of altering hi-fi settings and even changing CDs, all at the hands-free behest of the driver.

BMW offers a similar voice-activated telephone package on all of its models, with the sole exception of cabriolets and roadsters.

Spokeswoman Stefanie Koehler puts the price at about $350. The BMW version has a vocabulary of some 30 words and can access up to 40 telephone book entries in response to a spoken command.

Furthermore, the computer is fitted with enough memory to record a five-minute voice message, thus doing away with the need for a Dictaphone or notepad.

These two manufacturers from southern Germany may not dominate the voice-activation market for much longer with competition due to hot up in the near future.

Rivals Audi has announced it will be introducing similar technology as an optional extra on all models from the A4 to A8 before the year is out, while engineers at VW and Opel are likewise developing voice-activated systems of their own.

The greatest problems to be overcome in the development stage are disruptive background noises and discrepancies between regional accents, which require a great deal of fine tuning.

Meanwhile, in the United States, Cadillac's multimedia Communiport system offers a glimpse of the future in voice-activation technology.

Uwe Mertin, a spokesman for General Motors Germany, reveals Communiport will be entering mass production in the U.S. within the next two years although customers will have to wait rather longer before it becomes available in Europe.

The American system allows the driver to control not only the radio and telephone orally, but also the car's navigation aids. Further highlights include access to E-mail and the Internet, allowing occupants to keep up-to-date with world news, personal mail or football results.

To ensure drivers really do keep their eyes on the road, GM's on- board computer will read out vital information such as lottery numbers and the on-line weather report. So if a lone driver feels bored on long trips, he can always strike up a conversation with his car.

(DPA)