When planning the signaling for Port Dinllaen, I used the signalbox forum site to refine the design. This site has gone into abeyance, but I have retrieved the relevant pages and post here (obfuscated) as the discussions were so informative.
https://portdinllaenlines.com/port-dinllaen-signaling/
https://portdinllaenlines.com/port-llyfni-signalling-notes/
https://portdinllaenlines.com/tan-y-graig-signaling-notes/
https://portdinllaenlines.com/nantlle-signalling-notes/
