I've always been confused about the types and use of, switch/signal towers.:headspin: For me this is a very interesting link and along with the great pictures of switch.signal towers there is a little write up on the use of these towers. http://www.texasescapes.com/TexasRailroads/Railroad-Interlocking-Towers-of-Texas.htm I hope you enjoy the link as much as I did. See ya Ron