Editing Centralized traffic control (section)

===Signals and controlled points===
[[File:Uprr block signals.jpg|thumb|CTC automatic block signals along the [[Union Pacific Railroad]] [[Yuma, Arizona|Yuma]] Subdivision, [[Coachella, California]]]]

CTC makes use of [[railway signals]] to convey the dispatcher's instructions to the trains. These take the form of routing decisions at controlled points that authorize a train to proceed or stop. Local signaling logic will ultimately determine the exact signal to display based on track occupancy status ahead and the exact route the train needs to take, so the only input required from the CTC system amounts to the go, no-go instruction.

Signals in CTC territory are one of two types: an '''absolute signal''', which is directly controlled by the train dispatcher and helps design the limits of a control point, or an '''intermediate signal''', which is automatically controlled by the conditions of the track in that signal's block and by the condition of the following signal. Train dispatchers cannot directly control intermediate signals and so are almost always excluded from the dispatcher's control display except as an inert reference.

The majority of control points are equipped with remote control, power-operated switches. These switches often are ''dual-controlled switches'', as they may be either remotely controlled by the train dispatcher or by manually operating a lever or pump on the switch mechanism itself (although the train dispatcher's permission is generally required to do so). These switches may lead to a [[passing siding]], or they may take the form of a [[crossover (rail)|crossover]], which allows movement to an adjacent track, or a "turnout" which routes a train to an alternate track (or route).