Traffic Signal Controller
General
The controller is the "brains" behind every traffic signal controlled installation. The controller literally controls the way the signals appear, in what order and what the timings are. It can also monitor the detectors and lamps for faults and enact safety protocols in the event of a problem.
The Basics
In laymans terms there are three main parts to a controller which control the way it works;
> EPROM:
This controls which lamps operate and when, how the controller reacts to detector inputs and all the safety critical information such as lamp monitoring and detector fault monitoring conditioning.
> Inputs and Outputs:
These form the way the controller behaves and inputs demands from detectors on street, such as loops or pushbuttons or other traffic controllers. It can also output signals to other controllers, for instance Local Linking, which can be used to hold off other junctions or pedestrian crossings from changing until the controlling junction has changed stage.
> Lamp Switch Cards:
These are the actual components which control the appearance of the lamps on street; there are three lamp switches per phase and usually either four or eight phases per card. The red obviously controls the red lamps of a phase and may be used to control secret signs. The amber controls the amber signal, or if a pedestrian phase, the WAIT lamps. The green controls the green aspects and other facilities, again such as secret signs.
see also: Traffic Signal Controller Types
