Don:
To expand on the reply from Steve Holding about the signal system and types of signals, if you can obtain a copy (or copies) of the alignment charts for the territory you are interested in, these are usually a good reference for the location and particular
type of signals used on a territory. An exception to this is where signal bridges were used. Because of space limitations on the drawings, signal bridge territory shows the signal bridges themselves, but omits the type of target, since there is just not
enough room to show all of them accurately.
CB&Q used virtually every type of signal. The most prevalent were searchlights, and vertical 3-color lights. They also used triangular 3-color light signals in the suburban territory from the 20's to the 40's. Before light signals, the earliest ABS used semaphores,
as well as Hall 'disc' signals. Virtually all semaphores were 60 degree lower quadrant, and these were used for train order signals as well as automatic block signals and at interlockings. CB&Q began using color light signals in the early 20's, and began
a fairly aggressive program to replace semaphores in most territories. There were exceptions to this, like on the former LaCrosse territory where a few lower quadrant semaphores lasted into the early 60's. They also re-spaced signals as train speeds got
much higher in the mid 1930's, and on some territories there was more than one re-spacing.
I have seen the alignment charts advertised on ebay from time to time, and I would suggest you try to get one for the territory you are interested in.
Otherwise, if you are interested in the design/history/style of signals in a particular location or territory at a given time, contact me off list, and I can help you with most territories.
Glen Haug