This is a HO scale Code 83 left hand remote switch machine. You can use these to replace bad switch controllers or easily make your manual switches remote. Remote control switch machines allow you to throw the switch (therefore changing the direction of the rails) from a remote location on your layout, rather than on the switch itself. These units will fit on both Code 83 and True-Track & Snap-Switches. The switch machines are made by Atlas Model Railroad Co.