How do train crossing signals work?

Related questions

1. What's a red signal on a train?
2. What is Recfm?
3. What do train lights mean?
4. Do trains have red lights?
5. What is moving block system?
6. When approaching a railroad crossing with flashing lights you must?
7. What does run signal do?
8. How do automatic train signals work?
9. What is calling on signal?
10. What is fixed block?

Tags

1. #signal
2. #lights
3. #gates
4. #basic
5. #grade
6. #crossing
7. #consists
8. #flashing
9. #warning
10. #vehicles
11. #signals
12. #clears
13. #electronic
14. #circuit
15. #crossings
16. #train
17. #railroad
18. #attached
19. #island
20. #crossbuck
21. #devices