Thanks for the answer to my question, Vanark.
pdxdanmusic: after reading on howstuffworks, powerline networking would not seem to suit our needs. We only have/use one laptop computer in our home. Our usual second floor computer room gets a little cold in the winter for my wife (off-the-grid home/passive solar heat and wood stove on first floor), so I want to run that long cable from our router on the second floor down to the first floor, with the same laptop. Thanks anyway for the suggestion. Need to start off-gassing that long, new cable now, so it will be ready for in home use for my sensitive wife by the winter time...