Nigel, using relays in parallel with the servo ( or even other means of operating the tiebar) assumes that both will work at the same time. I have known solenoids not to move but separate methods of frog switching/ direction indication does , so either a short on the frog or incorrect indication. To me, the only real way to get correct indication / frog switching is based on tiebar movement meaning some form of switching from thet iebar = micro switches