What activates a train signal?

Related questions

1. What do train signal lights mean?
2. Do trains have traffic lights?
3. What is a Signalling failure?
4. What is a subsidiary signal?
5. What is fixed block?
6. Do trains have red lights?
7. What is fixed block Signalling?
8. What is signal overlap?
9. What is wayside railway?
10. What is a shunt signal?

Tags

1. #activate
2. #lights
3. #before
4. #basic
5. #crossings
6. #consists
7. #seconds
8. #train
9. #signals
10. #island
11. #flashing
12. #clears
13. #circuit
14. #arrives
15. #signal
16. #crossbuck
17. #gates
18. #attached
19. #about