Truth be told, my miniscule branch terminus (provisionally nicknamed "Tinories") probably wouldn't have had any fixed signals in 1840. All that would have been needed to control the trains at that time were a pocket watch (so that a train could be given a five or ten minute start along the line before the following train was allowed to depart) and some red flags for the railway policemen to wave frantically in an emergency. But I've always had a soft spot for the rotating disc signals used by companies like the Great Western and the London & Croydon.
It's very easy to build a rotating signal: you just need a stick, a disc and a drop of glue. In my case I used a length of skewer, collected during a visit to a posh burger joint, and the flat head of an office drawing pin:
I wound some copper wire around the pole of the signal to make a bracket for the cam mechanism that was going to turn the post through 90 degrees. This was easier than I expected - I just had to use a pair of pliers to keep squeezing the (reasonably) soft and pliable wire into the correct shape:
Then I glued the wire bracket to the post, remembering to glue it at 45 degrees to the face of the disc so that the cam would be able move the signal into the two positions required (disc facing the driver for "Stop", and disc turned sideways though 90 degrees for "Go"):
All that's needed is a hole drilled in the baseboard to hold the bottom of the signal post, with just enough slack to allow it to turn freely. I added a small length of brass tubing at the bottom of the signal post just to make the arrangement look a bit more visually interesting (and because I've had it in the spares box for years and never found a use for it before):
I used a coffer stirrer rod to operate the signal, with a piece of copper wire running through the bracket to move it from side to side:
And that was it. Surprisingly simple and effective, even if I do say it about myself.
Oh, and does it actually work? Of course it does: