by Nasadowsk
ABB's FL-9 rebuilds used to be able to sense the front shore comming off the rail and reduce power at the right moment to keep the rear one from arcing. I've seen M-7s arc though - I wonder why BBD or Mitsubishi or whomever didn't do it on the M-7s. Unless ABB has a patent on it? 
Though I think the DMs do that trick too.
Though I think the DMs do that trick too.