The main line is made up of two independent circuits, in the shape of a dogbone but topologically equivalent to circles, and these are divided up into sections, about 30 feet long. Each track in the staging is in two shorter sections, about 12 feet long.
The branch line starts at a triangular junction with the main line. When the layout was tun on DC, to keep the wiring simple, the up and down lines were wired with opposite polarities. Since the only crossovers between them were at Bowling Green Junction (to allow trains from the bay to get onto the up line) and in the Fiddler’s yard throat (until I put one in the garden shed) it was fairly easy, by judicious use of microswitches linked to the tiebars of the points, to arrange for the correct polarity of current to the yard tracks. When I added the crossover in the garden shed, I arranged a short section of track in the down line (including the crossover point) to be fed alternatively from the down feed or the up feed, switchable by a toggle switch with a centre-off position. This is because the purpose of this crossover is for manually fiddling around with trains, and it is not in general use, so nothing complicated needs to be done.
However, now that the layout is controlled using DCC, I have changed the polarity of the up line, and use a DCC reversing module to control the third leg of the triangle. This may cause problems if I try to run a 12-coach train with pickups on all coaches along that track, but if that happens I shall sort out some alternative arrangement with the reversing module.
The biggest problem on a layout this size is voltage drop. I use 7/0.2 (7-strand 0.2 mm diameter, rated 1.4 amps) cable for droppers from the track to the section busbars, which are 24/0.2 (24-strand rated at 6 amps) cable, to avoid voltage drop. I also use 1 mm diameter single strand cable to connect the two control panels together. All cable was obtained in 50 metre or 100 metre reels from my local electrical wholesaler.
All track feeds are colour-coded. I used the resistor colour code (0=black, 1=brown, 2=red, 3=orange, 4=yellow, 5=green, 6=blue, 7=violet, 8=grey, 9=white) modified to cope with the colours I was able to obtain, so the rails are coded red, orange, yellow, green. blue, violet, white, pink as you go from the front (garden side) of the layout towards the fence. The rails in the staging are coloured differently.
Originally, I built a control panel in plywood strengthened by softwood, using rotary switches, plugs and sockets: this was inconvenient as it had to be installed before every running session and removed afterwards. I have since replaced this with two panels constructed from Perspex using toggle switches (DPDT with centre off). These are left outdoors all the time. Apart from the panel at Fiddler’s Yard, the track diagram is not painted on them, as it is pretty obvious what’s what.
There are three ways to control the layout
This picture shows the Phase 2 switchboard and distribution panel. The wires at the left are the power supply (8 wires for 2 independent supplies for each loop), and the switched power is taken to the matrix of 20 mm. M6 set-screws at the right, from which 4-core 6-amp cable takes it to the track. The wires are crimped and soldered into 6.7 mm eyelets to fit over the set-screws, and into blade connector receptacles for the toggle switches.