The steam preservation group at Portsmouth would have a semaphore signal, so I've added a Dapol motorised signal. The original plan was to use a Ratio kit and a servo, but the N scale Ratio signal arm looks so flimsy where the wire would attach that I didn't see it lasting long.
The 1st Dapol signal only lasted 10 minutes. I tightened the plastic nut on its body - by hand, as stated in the instructions - and there was a crack. A glued joint had failed and it opened to two halves. All attempts to repair it failed.
The new one is now installed. The plan to operate it is to use a relay driven by a DAC20, so that the relay operates on BOTH Thrown and Closed. It will not be possible to know the aspect - but with turnout feedback, as long as it does always change state when commanded, Traincontroller should only send commands when it changes so it should stat in track to the PC.