TTSSP2 Sensor Signal Starter Pack 3 AspectA 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 DC as well as digital DCC and are fully Layout Link compatible, so easy to link Mimic lights and switches on a Mimic panel for control, signal display and train position indication with just a