Net goes magnetic
IT SOUNDS like a great idea: using ordinary power lines to carry Internet traffic. But the speed at which power lines can carry data has been limited because the transformers in substations can mangle the signal.
Now a Texas company says it has the answer: instead of piggybacking data on the electric current, it uses the magnetic field the current generates to guide a microwave along the outside of the cables.
Media Fusion of Dallas, Texas, was granted a patent for the idea in November. Inventor William Stewart, the firm's chief scientist, says the magnetic field acts as a waveguide. In Stewart's scheme, the signals are generated by a maser, a device that produces microwaves in the same way that lasers produce light.
Stewart says the system can transmit many megabytes of information per second, compared with about 1 megabit per second using electric current as the carrier. The latter is seen as uncompetitive in the face of high-speed phone line access (New Scientist, 18 September, p 13).
In the new system, fibre-optic lines will feed Net data to control centres at electrical substations, where it will be translated into microwave pulses that are sent to the subscriber's power line modem. The company has made the system work in the lab and plans to start large trials in the US soon.
Kurt Kleiner
From New Scientist, 25 December 1999
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