Most of what we know today are circuits that use semiconductors. This article describes some "vacuum tubes" that may be applied to computers of the future! http://www.popularmechanics.com/technology/a23759/micro-vacuum-tubes/?src=nl&mag=pop&list=nl_pnl_news&date=110916 73, GJ Gerry Jurrens N2GJ mailto:n2gj at amsat.org