We've recently been having unreliable communications with SCINI over it's tether line, and have tracked the problem back to our power supplies. This photo of an oscilloscope shows the alternating current input to the power supplies: usually this is a very thin and smooth sine wave, but the interference has blurred out the top of the waves. We use an ethernet over power system to communicate over our powerlines (very similar to the HomePlug residential product), which itself communicates with tiny pulses on top of the larger 60 hertz (60 times a second) sine wave; this kind of blurry noise interferes with the data pulses.