A comparison between two popular DCC Centrales

The ROCO Z21, currently the most popular digital power station on the market. And believe it or not, not even the most expensive either! Despite the fact that the power plants are full of ZIMO technology. Zimo is one of the better brands when it comes to digital, which is probably why the Z21 controllers are so popular around the world.

But now where does that come from? They are just square boxes that a digital DCC and Motorola voltage comes out of. Very exciting, that’s not what all power plants do….. And yet Roco has done a very smart job with the Z21 products, and often one smart move is enough to leave the competition behind.

Clever marketing of the Roco Z21

Roco and Fleischmann are two very old traditional brands. They have been making the finest model trains for decades and provide quality products at a neat price. In the digital field, however, they have always had to rely on technology from specialists. After the two brands merged into ModellEisenbahn München, it was decided to use the technology of Zimo, like ME also an Austrian brand. Zimo may not be a market leader in the digital technology field, but it is lord and master when it comes to technology and quality.

Well combine the name and quality of a brand like ZIMO and give it to a marketing team that understands how the current market works. They too saw that the league was asleep, there had been hardly any development for years and old concepts were being milked. The result is a Digital Power Station in a black box and a smaller brother in a white box.

Yes, I agree, the color choice is polarizing in the current zeitgeist. But luckily I don’t hear anyone talking about Roco having to go canceled….

The 10835 Multimaus

Roco Z21 Starter Set, where everything begins

Right there lies the marketing genius of the Z21. Whereas the competitors just put simple and light hand controllers in their starter sets, which you can’t do anything else with apart from controlling the starter set locomotive. Does Roco choose to put in a Light version of the power plant, along with the no less popular Multimaus hand controller.

So in addition to the Multimaus, you have a stripped-down version of the control unit that you can do more with than the competitor’s starter sets….. Clever? Thought so, read on quickly!

Entry-level digital power station called z21start


The genius of the white z21, yes with lowercase z, is not only in the fact that you already get it in a starter kit. By the way, through a starter set, the power plant is virtually free, if you add up the price of rolling stock. Small consumer tip, as the z21start is also sold as a Basic Digital set for €267.90(click here to view this product). But again, I digress too much 😛

The genius lies in the fact that you can go digital without spending a fortune already. And can already expand the basic set with additional hand controllers. And when you buy the WiFi package 10814 with it, you can control all your trains, turnouts and signals with the very inventive Roco Z21 app.

Currently, you can already do more with the white z21start than with the other starter set units such as the Piko SmartControll Light, Uhlenbrock Daisy II Digital Set or theMarklin Mobile Station (here you still need to buy a Gleisbox).

But it doesn’t stop there. You can also use the z21start to control your model railroad with computer software like iTrain! The only thing you need to buy besides a license for the software are occupancy detectors. Note that the limitation of the z21start is in the total number of busy signals possible and there are 160. If you need more busy signals then you can upgrade to the black Z21.

To access the z21 from your computer you need to set the LAN connection between the z21 and the PC to a static IP address. A dynamic IP address works only in conjunction with a WiFi packet.

Workshop iTrain

Did you know that we provide basic iTrain training?

With us you can take an online training course, to learn to automate with the Roco Z21 and iTrain. For only € 89.95 you get no less than 10 lessons that teach you step by step the basics of driving with iTrain 5.1

Is the Roco z21 even a starter set control unit?

Certainly it does, because even though it all sounds nice there are some considerable limitations to the white z21 compared to its big brother, the black Z21. An overview of the pros and cons:


  • DCC and Motorola
  • XpressNet for hand controllers (Multimaus)
  • R-Bus for occupied detectors
  • POM Programming
  • LAN connection for computer (via router)
  • B-Bus for boosters


  • Weak power supply for 3/4 trains
  • R-Bus can only accommodate 160 detectors
  • No LocoNet
  • No CAN bus
  • No RailCom
  • No programming output
  • No adjustable track voltage

Weighting Nutrition

So yes, the white z21 is far from fully deployable. Still, it is certainly not a wrong purchase! If you want a simple hand-controlled model layout, the white z21 will suffice. And that weak power supply? That one is easily replaced with a heavier power supply from Meanwell. Such as the SGA40E15 or the SGA60E18. Then as with the black Z21 you can just load the booster up to 3A. You do miss the ability to set the track voltage, which is why you make the choice up front whether you want to go for 15V or 18V.


One word, worthless. To program, I find this function really not doable. However, there is 1 option where it does work, and that is when you program POM via Decoderpro from JMRI. POM programming is a bit like sitting on the couch and asking your partner in the kitchen to make you a sandwich. With any luck, she walks into the room with a sandwich, usually you didn’t hear you. With a programming output, communication is two-way, or in other words, your partner yells from the kitchen that you can go ahead and do it yourself…..


Is this a problem? No way, I then recommend purchasing the SPROG programmer to program your decoders. No hassle and always works….

Computer control

He was not made for it, but then again he was. Basically, it is and always will be the Z21, but with a little less components. What it does have is the R-Bus, which you can use to connect occupancy detectors. But then you need the WiFi Package, otherwise you can’t connect it to the computer.

Because you can only fit 160 detectors on the R-Bus, it is only suitable for small model railroads. Also, R-Bus is not as free as LocoNet so you are really stuck with two products; the Roco 10819 X16 or the YaMoRC YD6016RB-CS

Only these two busy signal modules can be used on the R-Bus of the z21start. so you are somewhat limited in the choice and number of detectors. Nevertheless, this is certainly not a wrong way to automate.


Enabling the z21

To connect the z21 to the computer you need an enable code. It comes with the 10814 WiFi router.

Are you buying the 10814 from us? Then just bring your z21 and we will perform the enablement for you!

That’s the service of DTS!

ROCO’s flagship Z21 digital power plant


And rightly we think, now we already told that the z21 (white) could do a lot, the black Z21 is the power station that has no limitations! And in terms of technology, better than this does not exist at the time of writing (though it is coming). The competition knows this, and new power plants are working hard to take on this powerhouse. Besides the hybrid Dinamo system, the black Z21 is really our best seller!

Online training course Z21 Basics

Did you know that in our DTS Academy we have an Online training course on the Basics of the Z21? In 3 lessons we will show you how to connect the Z21, use the software and give you a tour of the Z21 App! And all for only €24.95!

With the purchase of the black Z21 PBX, you get this online training for free!


So what makes the black Z21 better than the white one?

Above you see Roco’s standard comparison chart, a lot of tough terms that you can do pretty little with. Because nice all those names, now what can you do with them all? First, what does the Z21 now have more like the z21?

  • Wifi package included
  • Adjustable power supply
  • Programming output
  • Sniffer bus
  • LocoNet
  • CAN Bus
  • ZIMO MXULFA built in, to flash Zimo decoders with sound or to update with firmware.

Ok very nice list, and yes that is more than there is on for example the ESU EcoS or an IntelliBox. But what is the use of this? Explaining that, I’ll pick out the main benefits!


Personally, I think this is the most important one. Because LocoNet can do much more than Xpressnet or R-Bus. Anyway, LocoNet is already more versatile to build, you may just split the cables with LocoNet. You can also use LocoNet hand controllers, which can do more than the Xpressnet hand controllers such as the Multimaus. What is by far the most important advantage is that you can connect 4096 occupancy detectors via LocoNet. This also makes the Z21 usable on very large model railroads!

Connect directly to the PC via LAN

The Z21 comes standard with a WiFi router, and does not need to be enabled like the z21. You can also omit the router, but I personally recommend always using the router. It gives just a little more stability when it is between your computer and the Z21, than when everything runs through the home router that the whole family uses.


The CAN is a cool feature of the Z21. Via CAN, the smart Single booster and Dual booster are connected to the Z21 central unit. These transmit all their information via CAN and synchronize flawlessly with the central booster. Also, you can now start using RailCom feedbacks over CAN. This gives an extra gadget on the model railroad where the locomotives tell who they are and where they are. Handy if you work without a computer.

Adjustable power supply

Finally a power station where you can specify in ed app how high the outgoing voltage can be. My personal preference is 16V, however, 18V with the current generation of micro- and nanodecoders is already no problem at all. The convenient thing is that when you want to change from scale Z (12V) to N/H0 (5-18V) all you have to do is adjust the voltage in the app. Both the central controller and the smart CAN boosters take over this almost immediately.

Then there is also that Xtra Large, the Z21 XL Series!


The white and black Z21 are intended only for Z, N, TT and H0 scales. For large scales, the 3A internal booster is not heavy enough. For this purpose, Roco created the XL line. An XL version of the Z21 but with a 6A booster and a higher voltage of 24V.

Do not use the XL not with small bowls! The booster switches off less quickly in the event of a short circuit, which can cause damage to your moving equipment. These do not particularly like a short-circuit current of 6 amps. Doing so will void your warranty!

Finally, in conclusion of yet another whole story

I hope this article will give you some clarity on the various Z21 versions. In a language easily understood by the beginner. Still have questions, or want to purchase the Z21?

Then you have come to the right place at DTS! We work a lot with the plant ourselves and know the products inside and out. This allows us to serve you as a customer with a Z21 workshop, online training, and support through our online help desk!

That’s the service of Domburg Train Support

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