Colour light signalling
Heathcote Electronics makes the MAS Sequencer and IRDASC-4 to control two, three or four-aspect colour light signals solely by the movement of trains. The starting point is the MAS (Multi Aspect Signal) Sequencer. It is positioned after the signal so that when the front of the train reaches it, the signal automatically changes to red. This replicates how things work on real railways, where the signal also changes to red as the train reaches a track circuit past the signal. When the entire train has gone past, the MAS Sequencer’s timing routine begins. If your signal has four aspects, the red remains lit for a third of the timing sequence, after which the yellow lights, then the double-yellow and finally the signal returns to green. The timing method used by the MAS Sequencer allows a two, three or four-aspect signal to be controlled by one detector. Connecting power to the MAS Sequencer is also very straightforward. The 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 using time, 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 had the train cross its detector. At this point it will change to yellow. The MAS sequencer controls the last signal on the line and an IRDASC-4 controls each preceding signal. A single wire links each board from the S (send) terminal back to the R (receive) terminal. The wire between these terminals sends the signal aspect information along the line of signals.