[Doug]

How do I wire this up so that a loco can pass from one section to another that is wired inversely without causing a short-circuit?

The two sections have to remain as they are outside of this drawing.

Is there a way to automate the polarity switching using a reversing-loop module when the points are switched to the crossover?

What is the simplest solution without using an intelligent booster?

 

[Doug]

OK, to make it logical - they are in the same direction on the other end of the layout. The inner line crosses over via a figure of eight and therefore switches direction at this point. Having the link between the lines here allows a change of direction of the train.

 

[Doug]

Will this do it?

Adding an auto-reverse Loop Module to the track at 'B' and to the reversed section at 'A'.

The blue dots show isolated joiners.

The auto-reverse unit detects the polarity switch when the points are set to the cross-over.

 

[Doug]

OK, I've solved the problem. I bought a reversing module and connected its output to 'A' and its input to the the DCC BUS. Isolated joints as shown by the blue dots. It works fine as long as the reversing section is as long as the length of a full train. Initially I had the reversing section too small and I had some problems with some Hornby coaches shorting one one side of the set-up when the loco was on the other.

I actually bought two quick response solid-state reversing modules for about $40 each from Tony's Train Exchange. Click here for more info. The second I'll use for a turntable. I mounted them in a clear VHS video box that is mounted under the layout. This way, when the box is closed, I can see the LEDs that indicate if power is being received and also the LED that indicates the polarity of the system - a useful debugging tool.

BTW, Tony's Train Exchange sell Lenz decoders for less that you can get them in Europe (including transport back to Europe)... go figure