If anyone wants to make working models of the 3-position, upper-quadrant semaphore signals used on the Eastern line through the hills, here are some circuit diagrams to obtain 3 positions from a Tortoise point motor.
Please contact me if you would like a PDF of the above circuit.
No, I don't plan to install semaphores on my layout - I just experimented with the wiring for fun. I am sure similar wiring diagrams have been published before but I couldn't find one on the web.
Ready made S scale are available from the US (NJ International) but the are made "mirror image" compared to WAGR signals as they drive on the other side of the tracks.
Another alternative to a Tortoise is a servo motor as used for radio controlled models. There are commercial units using servo motors which can be configured to operate 3-position signals (as well as points, boom gates, etc.). An advantage of a servo motor is that the operating speed can be adjusted, e.g. to make it slower, and the positioning is more precise than a Tortoise. However, the electronics to control a servo motor are more complex.