nyoung

Thanks that's very helpful in answering my question and the extra info on the 3 aspects is quite fascinating.

I have other questions which betray my ignorance of signalling practice in general so perhaps someone can point me to a good textbook on the subject?

But essentially does the shunting signal control the same length of track (block?) as its respective semaphore? But I assume in some cases where the semaphore is red the shunting signal shows green to allow a loco to back off its train etc.

Thanks again, really appreciate the wealth of knowledge made freely available.

Please can someone explain to me the purpose of the two different types of signals in this photo:

1. Big round searchlights
 

2. Small vertical 2 aspects

I have guessed that 1. is equivalent to a semaphore and 2. to a shunting signal but experts will know better!

Thank you in anticipation.

Nick