Imagine walking through the airport, looking for the nearest restroom. It appears that you have lost your way, and as there is no one in sight, you are unsure of what to do. In this future, however, you can simply look down at your handheld device and receive the required directions. You have only the fluorescent lights above you to thank.
Recently, a professor at the Massachusetts Institute of Technology has devised a way to transform ordinary fluorescent light fixtures into inexpensive data transmitters. Dr. Steven Leeb, has created these specially modified fixtures so that they can not only beam out illumination, but data as well. Dr. Leeb, who teaches circuit design, has accomplished this feat by changing the way in which the light fixtures fluctuate.
Normal fluorescent lights use a device called a ballast to control the current required to create light. The ballast makes the vapor inside the fluorescent tube ionize many times a second, creating a flicker that is invisible to our eyes. By modulating the frequency with which the light flickers it is thus possible to transmit data using the lights.
"The ballast," as Dr. Leeb claims, "is what makes the magic happen." While a normal light would flicker with a frequency of 40 kilohertz, 40,000 times per second, these modified lights will flicker with slightly different frequencies creating digital 1s and 0s.
"The trick is that our ballast moves the frequency around in such a way that the light doesn't flicker visibly," Dr. Leeb said.
So does it work? A demonstration is given at Dr. Leeb's company, Talking Lights, created in order to market the new device. He turns on a circular fluorescent fixture and enjoys examining the facial expressions of onlookers as Handel's "Messiah" pours out of speakers connected to a photo detector and processor. "People get the idea," he likes to say.
Nonetheless, according to Dr. Neil Lupton, president of Talking Lights, the process does not end with the lights.
The information sent out by the lights must be received and interpreted by some device. This can, for instance, be done by inexpensive photocells, whose size, including photocells, circuits and chips is only half as large as a pack of cigarettes. On the other hand, the information must be given to the lights in some manner.
This too, is flexible and inexpensive. A simpler method uses a microphone as audio input and a wire as a device to carry sound data to the lights, while a more complex method required lights to be wired together in a network they could be reprogrammed with ease.
The use of this technology is not limited to airports. Such a lighting system could be invaluable in subways, shopping malls and other highly populated complexes. Nor are the applications of this technology limited to giving simple messages and directions. Tests have already been conducted as to the potential gains of using such fixtures as aids to blind and brain-damaged patients.
A recent project sponsored by the National Institutes of Health and headed by Dr. David Burke, an assistant professor at Harvard Medical School and director of the brain injury unit at Spaulding Rehabilitation Hospital in Boston, examined the use of these Talking Lights with brain-damaged patients.
According to Dr. Burke, "the brain-injured can walk around, but they can't organize schedules or remember when to do things."
Thus each patient was given a handheld computer programmed with that day's schedule as well as the necessary locations.
As each patient would pass the light at a location, the handheld would recognize the signal given out by that light and cross-reference it with their schedule and location.
If for example, the patient should up for a test as expected, the handheld would recognize the light's signal as correct.
However, if a patient showed up at the wrong test or at the wrong time, the handheld would recognize the location as incorrect and give the patient voice commands regarding where to go.
The results of this study, published in the June edition of the Journal of Head Trauma Rehabilitation showed that patients who used this system relied less on directions from hospital personnel and arrived at their appointments more promptly than those without the system. Not too bad for a talking light.
