there used to be a really good section in the rulebook explaining semaphore signalling and things like station limits, home, section etc but im jiggered if i can find it now in the new on line book
this may be of some use though, the current RSSB 'handbook' which has some useful info in it
https://www.rssb.co.uk/rgs/rulebooks/RS521%20Iss%203.pdf