IRDASC-4 box

An IRDASC-4 is similar to a MAS Sequencer as it uses infrared detection to change its signal to red. The difference is that rather than working by timing, the IRDASC-4 sets its signal according to the setting of the next signal up the line. For example, after it has detected a train and set its signal to red it will stay at red until the next IRDASC-4 or MAS Sequencer up the line has both set its signal to red and when the train has crossed its detector. At this point it will change to yellow.