Specifications include, but are not limited to: support the following railroad interface input circuits: These relay circuits are interconnected from the traffic signal control cabinet to the adjacent railroad bungalow. A. Supervisor Circuit (SUP); A fault on this circuit will place the traffic control signal controller preempt input in an active state which will place the traffic control signal in all red flash. -This is the highest priority preempt input for the traffic control signal controller. B. Gate Down (GD), Island Circuit (ISL); Circuit is active when the railroad crossing gates are in the down position. This circuit being active will allow the traffic signal controller to service a limited number of vehicle phases (movements) while active. This limited service is sometimes referred to as the dwell phases. -This is the second highest priority preempt input for the traffic signal controller. C. Simultaneous Preemption (XR); Circuit is active when the railroad crossing lights start to flash and if provided, the crossing gates start their descent. This circuit being active should be used to turn on blank out signs when required. -This is the third highest priority preempt input for the traffic signal controller.