THE FRONT DOOR TO YOUR company's plant may soon recognize you in the same way that people do: through such unique characteristics as your voice, hands, eyes, and fingers. Biometric security systems, which are falling in price, could soon become a chief line of defense for companies trying to protect themselves against ever-increasing theft.

For about the past decade, reliability problems and high prices -- in the $5,000 to $50,000 range -- have held the domestic biometrics market to around 300 installed devices, most of them at government agencies. But advances in biometrics technology and growing concern about the security of vital data and equipment are now unlocking the door to widespread commercialization. "There is an increasing awareness of how much all of us are being ripped off or threatened," says Emily Ginsberg, vice-president of Fingermatrix Inc., in North White Plains, N.Y., which makes a product that utilizes fingerprints. "We are on the verge of much greater market acceptance." Prices could sink to $3,000 by year's end, she predicts.

Biometric systems, many of which are made by small companies, rely on distinctive physiological features. All of them operate similarly: A machine analyzes and stores the key features of a characteristic, such as the voice. When an individual punches in a personal identification number and then speaks, the computer checks that voice against the one in its memory. None of the devices are foolproof: A cold or a two-martini lunch can alter the speaker's voice and hopelessly confuse the machine.

That would cause considerable distress to an executive who couldn't get into the office on a Saturday morning. But the machines may be forgiven a few glitches if they keep thieves out. "At this point, people aren't stumbling over each other to place orders," says Russell Maxwell, a staffer at Sandia National Laboratories, in Albuquerque, where many biometrics systems are tested. "But that will change someday soon."