When we came back from Philadelphia on Amtrak last Saturday I posted to misc.transport.rail.americas a question about why there many short-distance power outages on the train ride - often 15-30 seconds when the lights and HVAC were off. I know it has something to do with voltage, frequency, and phase differences on different segments and various vintages of equipment. As of 10 minutes ago there were 77 posts discussing this matter with lots of technical explanations from seemingly quite knowledgeable people. There has been no thread drift - there are references to how it works on several other railroads but these shed light on the explanations, no sniping at other posters and very little negative slant. I got much more explanation than I wanted butit has been interesting seeing the discussion.