How To Advanced automatic reversing controllers

Advanced automatic reversing controllers

By Allan Gartner | September 1, 2021

Check out DCC Currents from the October 2021 issue of Model Railroader

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1) The PSX-ARFB. To use the DCC Specialties PSX-ARFB as a basic auto-reversing section controller (ARSC), just hook up two wires to the track bus (input on right side of photo) and two wires to the reversing section (output on left side). It has many more features if you need them. Photos by the author

In the April 2021 issue of Model Railroader, I wrote about DCC reversing sections. I briefly touched on some automatic reversing section controllers (ARSC) that are available. This month I will focus on ARSCs that do more than just the basic reversing functions.

Have no fear, because all ARSCs still work with as few as four wires – two to your booster and two to your reversing section. But some can control turnouts to balloon tracks, support transponding or RailCom, have built in electronic circuit breakers (ECB), report their status to Java Model Railroad Interface (JMRI), and yes, even more!

Reversing loop
Time and space. Whether using the PSX-AR or the DR5013, the cautions are the same. When using a slowmotion switch machine, make sure your sensing sections are long enough that the machine has time to line the turnout before the train arrives. Your reversing section must be longer than your longest train. Illustrations by Kellie Jaeger

Most ARSCs use short-circuit detection to automatically reverse polarity. This process can compete with ECBs and cause conflicts. If you plan on using ECBs to break up your booster districts for easier troubleshooting and will also be using an ARSC, I recommend looking for an ARSC that has a builtin ECB. You will then connect ARSCs discussed in this
column directly to your booster and not after any other ECBs.

Many DCC devices have various outputs that are known as “optically isolated, open collector.” Some of the advanced ARSCs are so equipped. I like these outputs because you can hook them up to almost any input device without fear of damaging anything (1).They depend on the input device or an external power source to provide power for them. Without either, you won’t measure anything with a meter.

The PSX-ARSC from DCC Specialties is both an ARSC and an ECB, but that’s not all. Its ECB has “adaptive load reset” capability, meaning it can sense sound-equipped locomotives and reset properly. Like other ECBs, it can automatically reset or be reset manually with a pushbutton. The ECB’s trip points can be set from 1.27A to 19.2A. You can also add an audio alarm for when there’s a short.

If you need to control a turnout for your balloon track, the PSX-ARSC can do that. It can line the turnout as the train goes around your balloon track. You’ll need a bit of isolated track on your balloon track that will trip the PSX-ARSC and give your slow-motion switch motor time to move (2).

If you also need to control the power routing of your frog, you can use the switch inside your switch machine, if it has one, to do this. It can control both slow motion (like a Tortoise by Circuitron) or snap (twin-coil) switch machines. You can also line the turnout with DCC accessory commands or push buttons.

The PSX-ARSC contains outputs for light-emitting diode (LED) indicators to monitor input/output power and status. For low amperage boosters, there’s a provision to kickstart its restart.

Finally, you can use a photocell to detect a train in a reverse section and turn off its power. This is useful for staging a train. You can use a DCC command to restart it. Note that if you’re using stayalive devices in your locomotives, the train will keep going for some distance, so don’t place your photocell too close to your turnout.

For a few more dollars, you can get the PSX-ARSCFB. In addition to the above, it can provide block occupancy feedback for shorts and occupancy and report it to your Digitrax LocoNet, Lenz ExpressNet, or NCE Cab Bus.

A PSX-AR can be used for back-to-back reverse loops that may compete with one another. This seems simple enough, but use with caution to avoid strange results.

DCC Specialties products are available from Tony’s Train Xchange.

The Digikeijs DR5013 is a European ARSC that has several features not found in American-made units (3). For example, it supports RailCom. It also has detection capabilities for three-rail trains. It can communicate with the rest of your layout and other Digkeijs products, as well as your computer, using LocoNet.

This ARSC also has an optional way of activating reversing. Usually this is done when the ARSC detects a short. It then reverses the polarity of the reversing section to correct the problem. If you don’t want to put even momentary shorts on your track bus, this ARSC has the option of using sense sections to reverse polarity instead.

It would be at home on any model railroad, particularly one where you want to automate your train operations or provide status to your computer running something like JMRI. You may want to download its manual to get a better idea of everything that it can do. It’s 32 pages long, but each page is concerned with a single topic. Just find the page that applies to what you want to do and follow it. The manual is in English, but it does contain a few terms that Americans might not recognize immediately. For example, “magnetic article address” refers to your turnout address.

If you use sense sections, the reverse section, not including the sense sections, needs to be longer than your longest train (2) – see my April 2021 column. Think about it; you don’t want the power-drawing sections of your train to be in both sense sections at the same time.

(3) The DR5013 isn’t equipped with an ECB, but it does detect shorts and can report this status to your automation system to tell your booster to shut down. See page 25 of the manual.

The DR5013
3) The DR5013. The Digikeijs DR5013 has a few features not often seen in American DCC products. This includes support for RailCom and polarity reversing triggered by sensing sections rather than a brief short.

Digikeijs products are available in the United States from Iron Planet Hobbies ( The Digitrax BXPA1 ( is an ARSC with an ECB (4). For layouts owners desiring automation, it can report track status over LocoNet to your computer or signaling hardware, and has outputs for occupancy and reversing section polarity. It includes support for transponding, reporting over LocoNet not only occupancy of the reversing block, but also which locomotive.

The BXPA1.
4) The BXPA1. The Digitrax BXPA1 works with trains equipped with transponders, which can tell your dispatcher not just which tracks are occupied, but by which train.

To implement transponding, you’ll need a transponder in the train to be identified. Digitrax decoders have transponders in them, or you can add a low-cost transponder to existing engines or rolling stock. You’ll also need block detectors that contain transponder receivers, like the BXPA1 and the eightblock BXP88. The BXPA1 uses Digitrax’s high-sensitivity current detection. It can detect cars equipped with resistors on their wheels as high as 22KΩ.

Track polarity signal.
5) Track polarity signal. A track polarity indicator for the BXPA1. You could use separate LEDs to show track polarity instead of a single bipolar LED as shown. Just hook up two LEDs like above, with one LED’s leads reversed.


Occupancy indicator.
6) Occupancy indicator. This is an example of an optically coupled, open collector output showing an external occupancy indicator for the BXPA1. Use a 330Ω, 1⁄8W resistor with a 5V power supply. If you want to use a 12V power supply, use a 1kΩ, 1⁄8W resistor.

Trip speed and level are adjustable for the reversing and power management functions. Be sure to download Digitrax’s KB1058 for advanced set up information from its tech support webpage.

The KB1058 says that an “appropriate” resistor should be used with the external status outputs, XR and XG. I found that a 470Ω, 1 ⁄4W resistor worked well. If you want the colors to be reversed, just reverse the LED. You can also use separate red and green LEDs (5).

The BXPA1 has an optically isolated detector output for occupancy indication (6).

The AR10.
7) The AR10. The NCE AR10 has LEDs that indicate the presence of a short and the polarity of the reversing section.

The NCE AR10 ( is both an ARSC and ECB (7). It has a trip current that’s adjustable between 1 and 10 amps, an adjustable short circuit response time, and a selectable manual or automatic short circuit reset. It comes with trip current set to 1A and automatic reset after a short. It also has an output for a remote LED that lets you know when the loop track attached to the AR10 is shorted.

I hope this overview has given you some insight into ARSCs that do more than just reverse track polarity. For a convenient link to all links in this and my other columns, go to

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