Joarel:
One of my clients used to use a power-line- based link for a printer app once. It was in the m and a dept of a large brokerage, and it was discontinued due to its security risk. I think that it operated at some low ascii speed at the time, but I'm not sure. Not very fast, in any event.
Superimposing both voice and data on power lines is an old "art" form. Some of the utility companies actually used to superimpose their order wires (internal voice and telegraph channels) onto their high voltage a.c. <yes, and even d.c. at one time> transmission lines, using a double-sideband a.m./f.d.m. technique. It did in a pinch I suppose. I believe that railroads did the same over some of their switch control and hot-box control lines in the past.
Other uses of this approach by the utilities have been for short distance messaging of SCADA information and other telemetry-like "keying" for load shedding.
RadioShack, in fact, borrows from this approach and has a voice intercom unit that works on a.c. I happen to have a set of them in my home, and although it doesn't approach DOLBY sound quality, it's good enough to get everyone to come to the dinner table. <I wonder if my neighbors are listening in?>
I know of one client situation where these intercoms didn't work out in the end, due to their facility manager's decision to reconfigure their internal power distribution, i.e., they had their load re-distributed onto two different power distribution units or pdus.
More recently, patents have been issued covering this technology. For an example of one such idea, go to:
invention.com
and see an interesting diagram depicting one inventor's view of the world. The prospect made in the document is that it will work for up to 60 miles (and beyond, with repeaters!!). Of course, it doesn't mention the data carrying rate, speed of the line, level of quality to be expected, etc.
I would imagine that all of these approaches would work best during power failures. How's that for a new spin on the last-mile OSP power nut? <grin>
Frank |
