A new security technology aims to replace conventional motion detectors and infrared sensing systems with an invisible field capable of sensing intrusions. Called InvisaShield, the patented technology creates a field of radio waves around objects and senses changes in the field caused by the intrusion of a conductive presence — a person or a car, for example.

The InvisaShield product is composed of a small box the size of a wallet and an antenna. Circuitry in the box sends radio waves to the antenna, which, in turn, creates a field of radio waves around itself and any object to which it is attached: such as a fence, a door, a window or cabinet.

The circuitry box also monitors the field around the antenna. Changes in the field activate alarm circuitry that can connect to audio alarms, access control alarm systems, and closed circuit television installations.

The cost of the system is approximately $500.

The new InvisaShield technology offers an alternative to motion detection and infrared systems, which can create high levels of false alarms. InvisaShield allows adjustments to the radio wave field to prevent false alarms or at least reduce them to acceptable levels. “The system can be set to recognize the presence of something that lasts longer than a certain number of seconds,” says Samuel Duffey, chairman of Invisa Inc., Sarasota, Fla. “A bird flying past a fence, for example, could be disregarded.”

It is also possible to adjust the size of the InvisaShield detection zone. According to Duffey, the system can be set to detect a presence as far as several feet away or as close as a few inches. In some cases, detection may not be important unless an object is touched, and the system can be set to that level of sensitivity.

In addition, the system can be adjusted to deliver an alarm immediately, after several seconds, after a minute, and so on.

InvisaShield's adjustability marks the real difference between conventional sensing systems and InvisaShield. A camera-based motion detector, for example, can be set to detect motion within a certain area of a video frame. But once there is motion, the system will alarm. Likewise, infrared motion detectors will alarm the instant the beam is cut.

InvisaShield technology has been used by the safety industry since 1997 to control parking lot gates, sliding doors, and other powered closure devices. “In safety, we have thousands of installations,” Duffey says. “The Pentagon, State Department, numerous airports, hospitals and civic buildings use the technology on parking barrier gates.”

The latest generation of this technology has been adapted to security needs. “This enhanced presence-sensing capability is likely to become the basis for a new generation of security products by eliminating the need for beams, lenses and emitters, which limit the performance of older-generation presence sensing technologies,” says Steve Michael, president of Invisa. “Our research shows there is a significant and growing market for a higher level of security than is currently possible with older technologies such as magnet and reed switches and infrared, motion and audio discriminating detectors. The new InvisaShield will provide security professionals with operational advantages such as increased design and application flexibility, larger and more dependable sensing zones, greater effectiveness, reduced false alarms and reduced maintenance and down-time.”

According to Duffey, InvisaShield's security technology is currently undergoing tests by a number of governmental departments and agencies.

“We have also received a formal invitation to participate in the fourth Force Protection Equipment Demonstration (FPED IV) at Quantico (Va.) this spring,” Duffey says.

Organized by the Department of Defense, FPED IV is May 6-8, and is expected attract an estimated 9,000 government officials and decision makers from the DoD, Justice Department, Transportation Security Administration (TSA), and other representatives of federal, state, and local governments.