In message 1134944455.694231@athnrd02, Ioannis
writes
On first thought, a funny connundrum. On second thought, a potentially
_very dangerous_ situation, because, IF, while S1 was tripped, a REAL
train came and tripped S2, you can imagine what would've ensued.

If it's a dual rail system then there are separate switches on each
track that have overlaid control on the signals.

--
Clive Mitchell
http:/www.bigclive.com