How to wire a DCC reverse loop with an auto reverser
Isolate a reversing loop with gaps in both rails and let an automatic reverser swap its polarity as trains pass, so there is no short circuit and no switch to throw.
- Time
- 2 hours
- Difficulty
- Medium
- Cost
- Moderate cost
- Steps
- 7
- Checked
What you’ll need
- A DCC auto-reversing module (for example Digitrax AR1)
- Insulated rail joiners or a razor saw Search Amazon for razor saw model railway
- Twin wire Search Amazon for 16 AWG twin wire
- Multimeter Search Amazon for digital multimeter
As an Amazon Associate we earn from qualifying purchases. The Amazon links go to search results, so you can compare what’s available.
Before you start
- The AR1 is for DCC only and will not handle analogue locos (Digitrax KB539).
- Power off before cutting gaps or wiring.
Step by step
-
Step 1: Understand the problem
In a reversing loop (also wyes and turntables) the rails cross over, so one rail ends up meeting the other and a train bridging the join causes a short. The fix is an isolated reversing section whose polarity is swapped automatically (Digitrax).
Next: step 2 -
Step 2: Make the section long enough
Digitrax says the reversing section must be longer than the longest train that will use it.
Next: step 3 -
Step 3: Cut the gaps
Gap both rails at both ends of the reversing section with insulated joiners or saw cuts, so the section is completely isolated.
Next: step 4 -
Step 4: Turn off track power
Digitrax warns that connecting an AR1 with power on may damage it.
Next: step 5 -
Step 5: Wire the reverser
Mount it near the gaps. For the AR1: mainline Rail A and Rail B to terminals 4 and 5; the two rails of the reversing section to terminals 1 and 2 (terminal 3 unused). For other makes, follow their terminal labels.
Next: step 6 -
Step 6: Adjust the trip current
The AR1's trip current is adjustable from 0.25 A to 8 A over about half a turn. Start at the mid point, with the heaviest train you'll use. Run it into the loop: it should trip once, at entry or exit. If it trips more than once, turn the screw slightly clockwise; if the booster shuts down instead, remove the train, let the booster recover and turn slightly anticlockwise. Repeat until it trips once.
Next: step 7 -
Step 7: Test both directions
Run trains through the loop both ways at slow and normal speeds.
Tips
- The auto reverser must react faster than your booster's short-circuit trip – that's what the trip adjustment is for.
- If you use detection in the loop, Digitrax says extra care is needed with grouping – read your detector's manual.
Questions people ask
Can I use a switch instead?
Yes – a double-pole switch can reverse the loop manually, but you must throw it at the right moment. An auto reverser removes that.
How much current can it take?
The AR1 is rated 8 A peak, 6 A continuous (Digitrax). Other products differ.
Sources
Checked 18 October 2026. We wrote this guide in our own words, using:
- Digitrax AR1 auto reverser instructions (digitrax.com)
- Digitrax AR1 product page (digitrax.com)
- Digitrax KB539: AR1 special considerations (digitrax.com)
- Digitrax DCS240 command station manual (digitrax.com)
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Printed from dcctrainautomation.uk/guides/wire-a-reverse-loop-with-an-auto-reverser/ · Checked 18 October 2026 · General information only. Follow the maker’s instructions for your own equipment, and keep mains wiring inside properly made, enclosed power supplies.