The turntable example is obvious if you think about it - If I rotate the turntable 180 degrees the train is now facing the way it came and when a train crosses from the turntable back on to the track it came from a short would be created unless something is done to avoid that. The other cases on my layout are not so easy to understand but essentially the same thing happens - there comes a point where a train will leave the reverse section and end up going the way it came - say clockwise to anti-clockwise (calling lines up and down on a tail chasing layout is not helpful!). This would also cause a short because the left rail is now connected to the right rail, that's fine when there are no train moving because the section is isolated from the rest of the layout. However a locomotive crossing from that section as it reverses direction will cause a short across that join.
To overcome this there are a number of electronic options which detect and reverse the polarity before an actual short occurs. I could theoretically use one unit for all three of these sections but that would mean I could only have one train in operation on any of those at any one time. So I used one unit for each section and one for the turntable
I chose to use three Hornby auto reverse loop modules (R8238) which are no longer available according to Hornby. However on the plus side Hatton's have them for a £12 each and they are so simple to use. My auto reverse sections are quite long so I can run long train over them. Note: you can't have a train that spans both ends of the auto reverse section as that would cause a conflict that even an reverse loop module cannot fix. However this meant I really needed to have two separate bus wires for each of these reverse sections and to identify them as distinct from the main bus I wrapped some thin wire round the bus wire - purple for one section and yellow for the other to match my track design. These auto reverse wires can then be connected to the reverse section with dropper wires just like any other track:
You can see on this picture that the reverse loop module just has one switch Select/Elite which actually depends on the power supply in use , Select is 1 amp and Elite is 4 amp, and that's important to know if you have an e-link controller (as in my case), as it is possible to power e-link with a 4 amp supply not just the 1 amp unit it comes with, so these units need to be set accordingly.
That's about it for wiring my layout, but there's still much more work to be done, and next time I'll look at what I have been doing in RailMaster to make managing my layout simpler