ELLULAR phones, the global positioning system and wireless alarm technologies have made it possible for hikers lost on mountains to contact rescue teams. But what about someone who is knocked unconscious in an accident or cannot make a distress call because they're being assaulted? 

A University of North Carolina researcher has patented a system that can send a silent distress signal along with the victim's location to emergency personnel.

The system is just one of several recently patented innovations that make use of the global positioning system, an array of 24 satellites orbiting the earth that transmit signals used to determine the geographic coordinates of a person or object with a receiving device.

Leandra Vicci, who directs the university's Microelectronic Systems Laboratory, got the idea for the distress signal after two attempted rapes in the university area last year. At staff meetings, some faculty members wondered aloud whether the women could have used their cell phones to summon help.

"A few days later it occurred to me that while that was a singularly insensitive comment, they were onto an idea," said Ms. Vicci, a physicist and engineer who also teaches in the computer sciences department at the Chapel Hill campus. "If that could be automated, how could it be designed to get a 911 response team enough information to go on?"

She knew that the components of her idea already existed.

"There is the global positioning system, and G.P.S. technology tells where you are to within 50 feet or so, and of course there is cell phone technology, so you could make contact," she said. "Two things were missing. One, to be able to tell the 911 operator in sensible terms where you are. The other thing is how to tell them what the problem is."

Ms. Vicci solved those problems by drawing on two other existing technologies. She designed a small device embedded with a G.P.S. receiver, a cellular phone chip, a microprocessor and a microphone. The device could be fashioned into a pendant, or into an accessory worn on a belt or harnessed to a horse saddle, a ski binding or other equipment that a person might be using when an accident occurred.

To pass on G.P.S. information to a 911 operator, Ms. Vicci turned to databases called global information systems. They let users enter longitude and latitude and get back street names and landmarks.

"It will give you a point on the map, and it could translate that into `this is in front of the Carolina Union, or 50 feet from the intersection of Ransom & McCully streets,' " Ms. Vicci said. "That solves the problem of telling them where the emergency is."

Once the pendant is turned on, "it's basically a G.P.S. receiver that's getting your coordinates on the fly," Ms. Vicci continued. "Once it's locked to position and get updates, it can keep quite current."

The receiver would also keep a log of the person's movements.

Some people have questioned whether the device would create a potential invasion of privacy, Ms. Vicci said.

"This information never leaves this unit unless you have an emergency, and at that point you want people to know it," she explained.

In a crisis, the system would be triggered with a yank on the pendant's chain. The wireless phone chip would automatically contact a geographic information system server. The microprocessor would transmit the G.P.S. coordinates, and the server would turn those into plain English and pass them on to a 911 operator.