Many DC elevator systems also included Mercury Arc Valve rectifiers: http://en.wikipedia.org/wiki/Mercury-arc_valve http://en.wikipedia.org/wiki/Mercury-arc_val

Many DC elevator systems also included Mercury Arc Valve rectifiers: http://en.wikipedia.org/wiki/Mercury-arc_valve http://en.wikipedia.org/wiki/Mercury-arc_valve They are still in use in some places and a few can be found in abandoned stations on the London Underground: http://www.eetimes.com/author.asp?section_id=36&doc_id=1319738 http://www.eetimes.com/author.asp?section_id=36&doc_id=13197...