some help please with semaphores

[bunkerrattmk2]

ok so i'm confused red boards/block distant home distant , yellow boards could some explain what should go where with a diagram please or direct me to one? thank you
ken

 

[BLACKWATCH]

This site shows how it works over this side of the pond, it may be the same on your side, have a look ......... http://www.signalbox.org/signals/semaphore2.htm