There was a fellow on here about four or five years ago that had libraries upon libraries of old Federal Signal manuals and parts lists and catalogs. I think a few members were able to successfully acquire items from him, but he flaked out in pretty short order. I really wish I could remember his name.
The Twin Beacon Ray is also known as the Model 11. It has two beacons that share a lot of parts with Model 14 beacons. However, only one of the beacons has a motor in the base. There is a chain that runs through the bar so that the one motor drives both beacons.
A Visibar is just a bare bar, upon which you can mount whatever you choose.
@shues hit the nail on the head.. the term Visibar is used in a general sense to mean the Model 11 to most people.. But Federal calls the Visibar in its literature the actual bar itself that the beacons mount to.