TTSS9 Sensor Signal Multi 3 AspectSS9 3 Multi Aspect Modern Single Lens Automatic Signal Fully assembled signal with built in sensor for OO HO Now you can add automatic signalling to your layout in seconds with new Sensor Signals. A sensor is built into every signal so there is no wiring or extra circuit boards etc. Just clip or wire the signal into your track for fully automatic 2, 3 or 4 aspect signalling which works just like the real railway! Best of all they work on both analogue