From the blog "Kelvinbank, a Caledonian Railway project."

Ok, I have sold my soul to the devil and created a you tube account. So heres my first go at doing a video and linking it through to here. If it doesn't work shout at me and I'll see what I got wrong.   Anyway, this is a proper signal on a plug in post. The mk 2 has a detent spring to hold the signal at the right place ( the mk 1 inchwormed up a bit ) and the signal bit is better. Those round rung ladders from MSE look the part, worth the effort needed to make them. Three out of five made, ge