(FORTUNE Magazine) – A high-tech gadget designed to keep drivers sober changed Dale Brooks's life. Arrested twice in five years for drunken driving, the 33-year-old Ohioan was given the choice of losing his license for two years or putting a device called an ignition interlock into his 1977 Camaro. About the size of a car radio, the interlock links a sensor that measures blood alcohol content to the ignition. A driver must blow a sober breath into the system, or the car won't start. ''Counseling helped me cut back on my drinking,'' says Brooks, ''but this made me stop.'' Already installed in thousands of cars, ignition interlocks are quickly catching on with judges and lawmakers. Ten states have passed legislation supporting use of the mechanisms for convicted drunken drivers. Some 21 other states have bills pending, and national legislation has been introduced in Canada. Says Ohio's Hamilton County Judge Deidra Hair: ''They're working better than anything we've tried in the last 20 years, including prison sentences.'' The early successes are spawning an industry. Three companies -- Guardian Technologies of Cincinnati, Safety Interlock of Monterey, California, and AutoSense of Hayward, California -- already are marketing the devices, and at least five others are working on their own versions.

Safety Interlock, which has sold 50 gadgets a month since it began marketing them earlier this year, expects yearly sales to top 80,000 by 1993. That's a small share of the nearly two million U.S. drivers annually arrested for driving under the influence. The companies expect the gadgets to catch on among trucking companies and other fleet operators. A bill is pending in New York to permit putting interlocks in school buses. Though the price of the devices is sobering -- about $500 each -- drivers can save on insurance. The Moore Group in Atlanta offers a 15% to 20% discount on some coverage in three states to drivers that install a Guardian interlock system.