Loconet, CAN, BiDiB, RS-Bus, Xpressnet, Ecoslink, B-Bus… the list is long. Beside the tracks using mostly DCC or Märklin’s Mfx/MM protocols, choosing a bus connected to the command station is often something we all go through for our layouts. And just as decoder interfaces, the market is a mess for beginners and experts alike… an overview.
Take the bus, but which one?
Just a reminder of what a bus is: it is a “network” used to connect several modules to the train command stations; this includes feedback modules, physical throttles and others. It can also be accessory decoders (points, signals), although those can also be directed connected to the DCC track signal.
Just as with DCC decoder interfaces (see my old article here), the manufacturers have to live (and sometimes caused) a set of completely different and incompatible bus solutions. What’s more, which bus(es) is (are) available for a specific command station depends on the manufacturer and/or the model of the command station.
More than 10 years ago on this blog, I was comparing Loconet and S88 here. Here is now a quick and slightly more exhaustive overview of the main different buses in 2024… get ready for a complicated ride.
Some notes beforehand:
- This includes personal opinions based on my experiences or readings
- “Common in” is not based on market studies, but from what I gather from manufacturers and forums
- “Modules compatibility in real life” indicates, as far as I know, whether if you buy a module for this bus, you’ll be pretty much assured it will actually work with your setup (ah yes, cause some don’t, that’s the problem).
- Some of those buses can be connected, through specific interface modules, to a computer, even without being connected to a command station. This is an advanced user case for people who are willing to control their layout through different computer connections (the command station as one connection, the bus interface as another separate connection). The advantages/disadvantages of these buses then remain in that use case, but it is true that this allows using a bus for which you don’t have a port on your command station directly.
Also, a few buses here are based on the CAN standard, which comes from the automotive industry. It is the “lower technical layer” of the bus system, and usually is a modern and reliable technology. However, it is important to note that CAN buses are not compatible with one-another, even if they share the same physical plugs.
Oh, and a word of caution: many of those buses use RJ45 ethernet wires, they are cheap and reliable cables. But in no way shape or form should you connect those bus cables directly to a computer network port, a switch, router or modem, or any other computing network equipment (risk of destruction of both).
S88, the old guy
Technically, S88 isn’t a bus, it is a serial interface, but for the sake of simplicity for us, end users, I include it here.
S88 is strictly limited to feedback modules (train present or not). It is a very simple chain of different modules. It is in a way one of the most universal systems due to its age: many command station have an S88 port.
Beware though, because the S88 protocol is intrinsically prone to interference, a new norm, S88N is now widespread. It is the exact same bus, but instead of connecting the modules with flat cables, they are linked with a standard RJ45 ethernet cable. Sometimes you can use S88N between modules, but have to use a simple and cheap S88N>S88 adapter to connect to your command station with the old port.
Common in: Worldwide
Modules compatibility in real life: Excellent
Technology: Outdated serial-type bus, uses flat cables, or RJ45 for S88N
Advantages:
- Modules are cheap and widely available
- Present on many command stations
Drawbacks:
- Very old tech, unreliable on large layouts and prone to interferences
- Strictly limited to occupancy feedback detectors.
Loconet, the commercial success
Loconet was developed by Digitrax in the US. It is a universal bus, for detectors, throttles and accessory decoders. That’s what I am using, because it’s easy to use and very common. However, the technology starts getting old too, and some people complain about unreliability on the forums (albeit not as much as with S88).
First thing to note about Loconet: it’s actually two different buses… Many command stations include a “Loconet-T” and “Loconet-B” port. The B port is reserved for loconet boosters. The T port is for all other modules except boosters. This is quite confusing for the end user. Some command stations only include the Loconet-T port (which is the default if “B” or “T” isn’t mentioned), meaning people try to connected boosters to it and it doesn’t work.
Also, there are different kind of implementations. From what I understand, Loconet requires paying royalties to Digitrax. Partial implementation of the standard doesn’t. This partial implementation is present on many European command stations, and is then called “Lnet” or “Lbus”. Although it is indeed compatible with many Loconet modules (except boosters), this is confusing for users.
Also, there have been some inconsistent developments. Uhlenbrock for example sometimes uses (used?) crossed Loconet cables, instead of straight ones, which leads to some incompatibilities.
Common in: US, Europe
Modules compatibility in real life: Good with some exceptions
Technology: Proven, but pre-2000 technology, uses RJ12 (old US telephone standard)
Advantages:
- Many manufacturers and lots of modules available
- Versatile, and relatively easy to use (depending afterwards on the modules of course)
Drawbacks:
- Loconet T vs. Loconet B bus is confusing for users
- Closed source, with royalties to be paid to Digitrax in most cases
Lenz’s XpressNet (X-Net/X-Bus), RS-Bus, Roco Roconet (R-Bus)
Now in all fairness, these are buses that I had to read about to try and understand what they are, and if there even are a few modules available. And to be honest, I’m still not sure it’s clear in my head (you are welcome to comment if you know more). The Z21 website also helps because the Z21 has both X-Net (X-Bus) and R-Bus.
- XpressNet is from Lenz, the creator of DCC. Also implemented by some manufacturers as “X-net”, which apparently is a bus mostly for command throttles. But the Z21 website states at least one feedback module that is compatible. Atlas and Horny also use XpressNet according to https://dccwiki.com/XpressNet.
- Roco’s Roconet (also called R-Bus) is Roco’s variation on the XpressNet, which seems to be compatible with Xpressnet throttles for the most part, but uses a different physical plug
- RS-Bus is also from Lenz (not to be confused with the R-Bus!), but it seems like a different bus, which apparently is dedicated to feedback modules.
Here’s my very personal thought on those: they’ve been around for long. If they work for you, great, I am sure they fulfil their purposes. But choosing one of those is to go for a relatively limited number of compatible devices, except if you have a Z21 and want the compatible modules from Roco mostly.
Common in: Europe, and UK/US for Xpressnet ?
Modules compatibility in real life: Unknown
Technology: Pre-2000 tech, different plug types for XpressNet, Roconet and RS-Bus
Advantages:
- Reliable for many long time users, from what I read on online forums
- Confirmed still relevant with presence of X-Bus R-Bus on the modern Z21 Roco command station
Drawbacks:
- Not really multi-purposes buses
- Rather small number of modules available, except maybe the new Roco Z21 ranges
BiDiB, the German newcomer
BiDiB is a modern bus developed mostly in Germany, and supported by a few manufacturers. It is very versatile, offers modern function, interference resistance and future evolutions. It is also I think an open standard.
Problem is: it’s mainly common in Germany. There are to my knowledge no manufacturers outside of Germany that produce BiDiB modules, or command stations with a BiDiB port. In fact, if the BiDiB website is up to date at the time of writing this article, only 3 manufacturers (and not the biggest ones, despite I am sure having great products) have BiDiB products: Tams Elektronik (which I know for some of their good decoders), Fichtelbahn and the OpenDCC project.
Is BiDiB the future, at least for Europe? Not sure, the market will decide but it’s way too early to tell.
Common in: Not so common, focused on Germany
Modules compatibility in real life: Unknown (supposedly good)
Technology: Modern, interference proof, uses RJ45
Advantages:
- Modern and evolutive
- Open Source
Drawbacks:
- Confidential number of manufacturers and modules
ESU EcosLink and Märklin CAN
Developed by ESU, as EcosLink for their own range, and for Märklin and its central stations as CAN. This is a relatively modern bus based on the CAN layer. There are not so many compatible devices, and above all: although technically similar, some modules for the EcosLink CAN can be incompatible with modules created for the Märklin CAN, and vice-versa.
Oh and also, plugs are a mess. There are 7 pin plugs on the command stations, but the modules (boosters, detectors) have 6 pin plugs, so you have to use the specific cable provided. Also, you can extend the bus with “hubs”, but those are connected to another 9-pin specific plug on the command station. Yeah, easy…
Common in: Europe maybe?
Modules compatibility in real life: Excellent (within ECOS or Märklin ranges), average (between ECOS and Märklin buses)
Technology: Modern CAN-based, uses (in my view impractical) cables with Mini DIN plugs with complicated different cable types
Advantages:
- Works well and easy to use if you stick to modules from (or designed for) the same brand
Drawbacks:
- Not that common, and tied to specific manufacturers, limited modules choices
- EcosLink and Märklin CAN modules actually mostly incompatible
Z21 and Zimo CAN
Same story here: a bus designed mostly by one (Zimo), and also widely used by Roco on its Z21 range. But again, in the end, they end up being mostly incompatible: it seems Zimo uses 30V on this bus, while Roco uses 12v. Apparently, some modules designed for the Z21 can simply be destroyed if they are connected to Zimo CAN because of this. And despite them speaking the same language…but not at the same volume.
Now it is a modern technology, rich and interference proof. But again, it’s really 2 buses with average availability for modules.
Common in: Europe
Modules compatibility in real life: Excellent (within Z21 or Zimo ranges), bad (no compatibility between Z21 and Zimo modules)
Technology: Modern CAN-based, uses RJ45
Advantages:
Works well and easy to use if you stick to modules from (or designed for) the same brand
Drawbacks:
- Not that common, and tied to specific manufacturers, limited modules choices
- Z21 Can and Zimo CAN actually incompatible
LCC, the NMRA offer for a standardised bus
Launched in the last 10 years, LCC is an open source bus technology, now standardised by the NMRA in the US. It uses RJ45, and has all the bells and whistles of a modern bus. It is developed in cooperation with the OpenLCB organization. But there are very few command stations worldwide or modules that are already compatible with it.
The future will tell if it works. My fear here: that LCC catches on, deservedly, on the American markets, but remains confidential in Europe and the rest of the world. Leading to another tech schism between model railroaders of different continents. European manufacturers are too busy defending their own proprietary buses, or supporting the German BiDiB.
Common in: US (too early too tell but seems up to a good start)
Modules compatibility in real life: Allegedly excellent
Technology: Modern CAN-based, uses RJ45
Advantages:
- Open source and free to implement for manufacturers
- Rich and future-proof technology
Drawbacks:
- Not know outside of the Americas, or standardised in Europe
- Relatively new bus, not many compatible modules for now
Buses ranking
Which bus do you need? I cannot answer for you. Mainly, your choice of command station will influence your choice of bus (although sometimes the other way around for existing layouts).
Also, if you intend to use a model train control software on your computer at some point, you don’t only need to check that it is compatible with your command station, but also with communicating with that specific bus of your command station.
My goal is not the “rate” the bus qualities, but to give an idea of their position if you’re currently trying to choose a bus solution. All in all, and based on what I know about those different buses, I have ranked them in 4 categories:
Legacy and not future-proof, but extremely common:
- S88
Still relevant and with good modules product ranges:
- Loconet
- R-Bus (Rocobus) in Z21 command station
Reliable choices if you don’t mind proprietary solutions:
- ESU EcosLink or Märklin CAN
- Zimo CAN or Roco Z21 CAN
Future-proof and open source solutions, which may become more common soon:
- LCC in the US (NMRA)
- BiDiB in Germany
Other buses not mentioned here are surely fit for their purpose, but I haven’t seen enough products or talks about them to mention them here.
Conclusion
I hope this short overview helps you a little. There are many great ressources online to understand more, including user forums. Make sure you check the compatibility of your devices with the chosen bus, carefully read the online manuals or websites before ordering.
But all in all: it’s a mess. The model railroading industry is way too small and divided by continent for the market to actually choose a winner by itself. Our only chance at getting a good, universal and modern bus solution is for everybody, from manufacturers to train organisations to come together. I am afraid this won’t come anytime soon, especially with the recent rises of LCC vs BiDIB vs CAN solutions. These may not be perfect, but all seems to be technically mature to satisfy most modeller’s needs…if only their proponents weren’t fighting over which one is slightly better.
So this is a plea to the NMRA, the MOROP, RailCommunity and all manufacturers to sit down at the table and to understand that, just as in other tech industries, standardisation actually helps develop a bigger market for everyone involved, instead of destroying it by cutting it into jealously kept small pieces… It’s time to do some cleanup in the model train bus aisle.
But in the meantime, whichever bus you choose, and after careful research: the good news is, you’re gonna be able to run trains the way you want!
So what do you think and which bus system(s) do you use? Also comment if there’s info you think I should add to this post.
Reminder: I am a hobbyist and these articles only represent my personal views. I am not receiving any compensation, in any form, from the brands or stores mentioned here. The product names, marketing names, and brands mentioned here are the property of their respective owners.
