Signal & Telegraph.....

A need for electrical (model) connection of signal cabins, telegraph and block signals was needed to complete the scene. Ducting in the form of timber boxed conduit was/is a trademark SAR feature. Connections between cabins, signals, relay boxes and also turnout motors were commonly run in these networks of ducting. 

A photo I took in 1978 of Adelaide Signal Cabin shows the ducting in use in the foreground.

Trim off the ducting supports to 5mm
with a pair of  side cutters.

Matchsticks pre-painted and glued
into a suitable size hole in the baseboard

I use prepainted matchsticks for the pillars in the ground placed 25mm apart and trimmed to 5mm high. Either balsa or stripwood was used for the box conduit at 1.5mm square section.

You can just see there is a duct fixed to the telegraph pole to left of the pictures - this is where the wires from the from the cross-arms on the pole run down through to the cabin. There were a lot of cases where there were bars of insulators mounted on the signal cabin and this ducting would not be needed because the wires ran directly from the pole to the cabin.

Sup-glue or Tarzan Grip together the ducting onto the supports. Paint in a dark grey/brown colour to finish.

Trimmed ready for the
ducting to be added.

once the duct is secured, paint
with a dark grey colour.

Telegraph wires were often run under bridges in ducting and fixed to the retaining wall and not on the ground. The ducting runs down the first pole, along the ground and up the other pole on the other side of the bridge.

This photo shows how the ducting connects the telegraph
poles either side of the bridge.

This was a common way of running the wires through narrow clearances.The bridge may be too low for the wires to clear or in this case, there was not enough room for the poles between the track and the concrete abutments.