Questions & answers

1. Operation with Smartphone, iPad, Tablet, PC, handheld devices

1.1 What is the name of the app for the controlling?

The app for Android, as well as for Apple, is called "Z21".

In addition, there is still a "Z21 Updater"-App for Android, that you can use to update the Z21 to the latest firmware version.


1.2. Where do I find the Z21 app?

The Android app is available for download from the Google Play Store. The app for iPhone and iPad can be found in the App Store.

1.3. Which iOS and Android versions are supported?

The app can be used in iOS 11 and above, and Android 5 and above (with min. 5 GB RAM).


For older versions the old Z21 app can be useds (blue icon with taurus loco). 

1.4. How can I transfer the data from the old app to the new Z21 app?

In order to export your data there are some possibilities. In each case, both, your layout as well as your locomotive database, will be exported.


Import for Android:

In the old app under "Settings" first select the menu item "Export". Then tap on the layout you want to transfer to the new app and choose the option "SD-card". Therefore your layout is immediately saved on your device. 
Now open the new app and open the menu item "Layouts". Tap the plus icon at the bottom of the screen and select "Import from SD card". All layouts saved on your device now will be listed. Select the desired layout and choose a name. After tapping "Import" the layout will be transferred. 


Import for iOS:

In the old app under "Settings" first select the menu item "Export". Then tap on the layout you want to transfer to the new app and choose the option "Share (e. g.: new Z21 App)". 
A window will opens with a choice of apps. Tap on the app icon of the new Z21 app. The new app opens and you can choose a name for your imported layout. After setting a name, the layout can   be found immediately in the layout management of the new app. 


Import via e-mail (Android and iOS):

In the old app under "Settings" first select the menu item "Export". Then tap on the layout you want to transfer to the new app and choose the option "E-Mail". 
Your e-mail app opens with your layout attached. Send the e-mail (to yourself). Open the e-mail app on your device and tap the layout in the attachement of the sent e-mail. A window opens that suggests several apps to open the file. Select the new Z21 app. The app opens and you can choose a name for the imported layout. After tapping "Import" or "Import and select" the layout will be transferred. 


1.5. What if my layout can not be found on the SD card?

In order for a layout saved in the files to be found by the app, it has to be saved under the follwoing path:

Internal storage - rocoZ21-layouts

Only if the layouts are saved in this folder, they can be imported into the app. 

1.6. Does the smartphone need to have a SIM card in it to operate the Z21?

No, to operate the Z21 with a smartphone it is not necessary to have a SIM card. The connection between the smartphone/tablet PC and the Z21 is established via WLAN.

1.8. Why in the Z21 settings is there another setting option on the stop button when these have already been called up in the app settings?

The setting option in the Z21 settings goes to the control centre via the stop button, whereas the app settings relate to the Stop button within the app. This means that the stop response can be set separately in both operating options.

1.9. Can I also export or program the entered CVs on the smartphone or tablet?

Yes, the CVs can be exported via smartphone or tablet, both using the programming track, and via POM. There is a separate programming screen in the app for this purpose.

1.10. How do I use a second smartphone in combination with the Z21?

Like the first smartphone, the second also communicates with the router: In the "Smartphone settings", "WLAN" section, you will find a list of the routers found, which should include the "Z21 ... wxyz" option. Tap to simply select this router and log on using the documents supplied with the Z21!

1.11. Can I operate a Lokmaus and simultaneously a smartphone and a tablet on the Z21?

Yes, you can connect up to ten smartphones and tablets, and up to 31 standard X-BUS control devices simultaneously. This means you can easily enjoy driving evenings with friends, with and without smartphones.

1.12. Can I also connect the Z21 to a normal PC or notebook?

Yes, this is possible on a Windows system. The connection is established via the LAN port (network socket) on the computer.

1.13. What PC operating system do I need so that I can connect the Z21?

Windows is required for the firmware update and for the advanced settings via the Z21 Maintenance Tool (see Downloads area). Z21 Maintenance can also be used on MacOS and Linux with the help of WINE, however. 

Alternatively, the firmware update can also be performed via the "Z21 Updater" app on Android.

If you want to use a PC control for the system automation, you can use the following programs, for example:

  • TrainController (Windows)
  • iTrain (Windows, MacOS, Linux)
  • Rocrail (Windows, MacOS, Linux)
  • ModellStw (Windows)
1.14. Can I also use the Z21 without an app?

Yes, you also have the option of operating the Z21 using a large selection of handheld controllers and various input devices. See also the overview diagrams in "All connections on the Z21", sections "X-BUS" and "LocoNet-BUS". For wireless controlling you can also use the Z21 WLANMAUS.

To configure the settings and for the firmware update, a connection to the app or to a PC is still required.

1.15. How do I set turnouts and signals?
  1. Using the app: creating all the necessary magnetic articles and signals. Turnouts can be connected to one another to create a track plan. 
  2. Using the PC: TrainController, iTrain, Rocrail or ModellStw.
  3. Via X-BUS or LocoNet port (e.g.: Z21 multiMAUS, IB-Switch, …)
1.16. I can easily imagine controlling a locomotive on a smartphone or tablet, but is it possible to control a complex track plan?

System components can be distributed and created in the app in multiple sections. Naturally, in comparison to a tablet, the smartphone is somewhat limited in terms of the smaller display. For large systems, PC control programs such as TrainController, iTrain, Rocrail or ModellStw. are recommended.

1.17. How much do the Z21 apps and PC software cost?

The Z21 app is free of charge, as is the "Z21 Updater" app as well as the Z21 Maintenance Tool for the advanced settings and firmware update.

For prices of the PC control programs, please refer to the manufacturer in question.

1.18. Does the Z21 work as a central database (“server”) with a locomotive library?

Most locomotive data is not stored in the Z21, but are stored in the app. In other words, it is not possible to access the same data using any control unit. On each device, the data must be recompiled (e.g. Z21 multiMAUS) or can be copied from app to app. Only the most important information on each locomotive/turnout is stored on the control centre for track signal generation, such as the format (DCC/Motorola) and the number of possible speed steps. For this reason, some setting options in the app are greyed out in offline mode.

1.19. Is it possible to use multiple-unit train controls together?

Multiple-unit train controls and trains can be compiled in the app in the "railway vehicle settings". The corresponding locomotives, the "traction settings" must first be configured. This is also carried out in the railway vehicle settings.
To do this, a certain circle should be defined. Then the time has to be measured how long it takes each locomotive to drive through it at a certain speed step and the values should be entered into the table. As many speed levels as possible should be used to enable an exact adjustment of the traction. 

1.20. It is possible to connect the Z21 and get going straight away?

Almost. When you have connected your new digital control centre and the WLAN router provided, you will need to register your smartphone on the Z21 and download the corresponding app via the internet. You can then place the first loco on the main track!

1.21. What are the meanings of the different colours and status conditions of the front LEDs?
  1. Blue static: Normal mode
  2. Blue flashing: Emergency stop initiated
  3. Red flashing: Short circuit, overload
  4. Green static: CV programming
  5. Slow green flashing: Decoder Update
  6. Violet flashing: Reset the Z21 to factory settings
1.22. What do the values in the "Programming settings" mean?

Reset packets (start): determines the number of DCC reset packets right at the start of the programming sequence for CV read/write. The higher this value, the more time the decoder has to restart.

Programming packets: determines the number of DCC read/write attempts in the CV programming sequence.

Reset packets (continue): determines the number of DCC reset packets between the programming steps.

For additional explanations, see also the Z21 Maintenance Tool User Manual (download area), chapter "3.2 Settings", and for technical details NMRA Standard S-9.2.3 Service Mode For Digital Command Control"

2. Interfaces

2.1 What are X-BUS, L-BUS and CAN?

X-BUS (XpressNet), L-BUS (LocoNet) and CAN refer to different systems for serial data transfer. The interface, device connection and protocol must belong to the same transfer system in order for a device to function.

2.2. How many X-BUS devices can be connected to the Z21?

The X-BUS of the Z21 supports the connection of 31 devices.

2.3. Is it possible to operate the LocoNet™ and X-BUS in parallel?

Yes, LocoNet and X-BUS can be operated in parallel/simultaneously.

2.4. What power supply can the LocoNet™ Bus stand?

LocoNet and the X-BUS ports on the front of the device are on the same power supply and are each only permitted to be loaded up to 500mA, i.e. in total 1000mA.

2.5. What is the contact assignment of the LocoNet™ port

The contact assignment on the L-BUS is:

Pins 1 and 6: +12 Volt
Pins 2 and 5: Ground
Pins 3 and 4: Data 

This is a solely LocoNet-T design without RAIL_SYNC signal.


2.6. Can a LocoNet™-Booster be connected?

Due to the LocoNet-T design without RAIL_SYNC signal, the operation of LocoNet-Booster is not possible.

2.7. Is it possible for RailCom® data to be both received and sent via the LocoNet™ connection?

The loco address detected using LocoNet can be sent via RailCom® to the control centre. The sending of the remaining RailCom® channel 2 data via LocoNet is currently not implemented.

3. Compatibility with FLEISCHMANN/ROCO digital components

3.1. Can the wireless multiMAUSpro be operated on the Z21?

The concept behind the new Z21 digital system is to use only the best and most commonly used technologies in the context of being futureproof. In the field of wireless communication, the WLAN standard has established itself on all smartphones and tablets without question. For this reason, our Z21 control centre does not have any ZigBee wireless module. As a result, no multiMAUSpro devices can be operated directly on the Z21 control centre. Using LocoNet a multiMAUSpro can be used via the multiZENTRALEpro , however.

3.2. Can the Z21 multiMAUS or multiMAUSpro locomotive data records be transferred to a smartphone and tablet and back?

This is not possible as the Z21 means that restrictions such as the number of available characters in the locomotive name or function keys, are a thing of the past. In the new locomotive data records on the Z21 it is possible to create far more information (long names, function keys, image, etc.) than was possible with the Z21 multiMAUS. For this reason, the formats are not compatible.

3.3. Do I need to replace any devices from my previous digital system?

The Z21 is a fully featured value control centre and replaces your 10761 or 10764 booster, or your multiZENTRALEpro 10832/10786.

3.4. Can the 10785 interface be connected to the Z21?

It is not possible to use interface 10785 on the Z21. The PC connection to the Z21 is made via LAN.

3.5. It is possible to connect the TWIN-CENTER or TWIN-BOOSTER to the Z21 via LocoNet™?

The TWIN-BOOSTER cannot be used, but the TWIN-CENTER can be connected to the Z21 in two ways:

You can configure the TWIN-CENTER as a LocoNet slave (FW V2.000, special option 844=1). In this case, the Z21 remains the LocoNet master and the TWIN-CENTER works as the input device. 

Alternatively, you can configure the Z21 in the Z21 Maintenance Tool (see Downloads area) as a LocoNet slave. In this case, the TWIN-CENTER remains the LocoNet master. This means that you can control your existing system both with the TWIN-CENTER and with the Z21 app on a smartphone, tablet and Z21 multiMAUS.

The track, and the booster, if applicable, should always be connected to the LocoNet master as only the master generates the track signal.

When connecting the Z21 and TWIN-CENTER, the following points should also be noted: 

To prevent both control centres sending the supply voltage to the LocoNet bus simultaneously, the supply voltage (pin1 and pin6) must be isolated from the rest of the LocoNet on the L-BUS port on the Z21. To do this, use the white "Z21 LocoNet slave cable" produced specifically for this purpose using spare part article number 136100. This cable is available from your dealer or online from the service and spare parts site at 

Using the wrong cable can result in the control centre being destroyed!

3.6. Can I used old FLEISCHMANN FMZ locomotives with the Z21?

Locomotives with FMZ decoders only will not be able to "understand" the track output signals in DCC or Motorola! Nevertheless, over a number of years, FLEISCHMANN has recently "added two-language" decoders FMZ/DCC to its range: If you have these types of decoder versions, the locomotives can be controlled using DCC !

3.7. Can I use the Z21 to control the Roco 42615 and FLEISCHMANN 6152C turntables, or are there any additional hardware and software components that are required?

For this application, the FLEISCHMANN turntable 6152C requires the Fleischmann-Turn-Control 6915, and the Roco turntable 42615 requires the Littfinski decoder TT-DEC-R. To do this there used to be - as previously described - a few tricks on the control process from the track diagram of the RocoMotion software control system. This cannot be transferred to that for Roco and in the Z21 connection the "TrainController" emulation software from the same development company, Freiwald.

For the Fleischmann Turn-Control 6915 we recommend connection via LocoNet.

3.8. Does the Z21 produce the "Railcom® cut-out" and are the ROCO Boosters Railcom®-compatible?

Yes, the Z21® can produce the RailCom® cut-out .

The new Roco Boosters (10805, 10806, 10807) are also compatible with RailCom® .

The old Roco Boosters can still be used, but like all previous boosters, they cannot evaluate the RailCom® signal. When driving over the cut-off point, the RailCom®cut-out means that micro short circuits can also occur. For this reason, when using the old Roco boosters, the RailCom® should be deactivated if possible.

4. Compatibility with third party digital components

4.1. Can I use the Z21 multiMAUS on the Z21 to control locomotives in the Motorola format as well?

Yes, this is possible! The critical requirement is that this data format must be selected in advance in the app for the locomotive setting. In addition to DCC, the Motorola I and II formats can be used. 
The speed step setting in the app from "Motorola" has the following meaning:

  • "14":    Motorola MM I with addresses 1 to 80, 14 speed steps and F0
  • "28":     Motorola MM II with addresses 1 to 255, 14 speed steps and F0 to F4
  • "128":     Motorola MM II with addresses 1 to 255, 28 speed steps and F0 to F4.

The expanded speed steps in this case are coded in what is known as "light trit" . 
Older MM decoders may not understand this format.
Regardless of whether the locomotive is controlled via the app or a hand-held controller, it is always accessed using the format set on the Z21. In other words: You can then also use the Z21 multiMAUS to control a Motorola locomotive.

4.3. Is mfx supported as well?

No, mfx is not supported.

4.4. Do I need a special system for the Z21 digital system?

No, all you need is a standard, digital model system such as FLEISCHMANN or ROCO.

4.5. Can the Littfinski digital components (e.g. turnout decoder S-DEC-4-DC, feedback modules for the s88 feedback bus) be used together with the Z21?

Littfinski digital components that support the DCC or Motorola protocol, can be connected to the Z21. Feedback modules for the s88 bus cannot be connected.

4.6. Can the Uhlenbrock 63880 "s88 LocoNet™ adapter" to connected to the Z21?

Due to the vast number of s88 building kits and various "craft projects," galvanic isolation from the LocoNet bus and track cannot be guaranteed. For this reason, as a precaution we need to state a categoric "No" in terms of the s88 adapter as well.

4.7. Can the Intellibox be connected to the Z21 using LocoNet™?

The Intellibox 1 can be connected to the Z21 in two ways:

You can configure the Intellibox 1 as a LocoNet slave (FW V2.001, special option 844=2). In this case, the Z21 remains the LocoNet master and the Intellibox 1 functions as an input device. 

Alternatively, you can configure the Z21 in the Z21 Maintenance Tool (see Downloads area) as a LocoNet slave . In this case, the Intellibox 1 remains the LocoNet master. This means that your existing system is controlled both with the Intellibox and with the Z21 app on a smartphone, tablet and Z21 multiMAUS.

The track and where applicable, the boosters, should always be connected in both cases to the LocoNet master as only the master generates the track signal.

When connecting the Z21 and Intellibox 1, the following should also always be observed:

  • To prevent both control centres sending the supply voltage to the LocoNet™ bus simultaneously, the supply voltage (pin1 and pin6) must be isolated from the rest of the LocoNet™ on the L-BUS port on the Z21 . To do this, use the white "Z21 LocoNet™ slave cable" produced specifically for this purpose using spare part article number 136100. This cable is available from your dealer or online from the service and spare parts site at
  • Using the wrong cable can result in the control centre being destroyed!
4.8. Why are the turnout addresses shifted by 4 with some turnout decoders?

This issue requires a longer explanation, whereby the term "turnout address" is used not only in connection with turnouts but also for signals and other magnetic articles:
Unfortunately, due a weak spot in the DCC specifications, different methods of mapping turnout addresses have arisen over time. In technical terms, the "turnout address" shown to the user on the DCC control centre is first "translated" into a combination of module address and port address and then output to the track. And it is precisely this "translation process" that is not standardised.

Each module address is assigned 4 turnouts ("ports"). Depending on whether the control centre starts counting at module address 0 or 1, the turnout address displayed in direct comparison is shifted by a value of 4. Due to the unsatisfactory specification, neither of the two counting methods can definitively identified as "incorrect" or "correct".
Roco has always numbered the turnouts from module address 0, whereas some other DCC control centre and decoder manufacturers start numbering at module address 1.

  • Roco: Turnout address = module address * 4 + port address (port address: 1…4)
  • Third party control centre: Turnout address = (module address-1) * 4 + port address (port address: 1…4)

If a turnout detects that it is being addressed with module address 1 and port address 1, for example, with a Roco control centre it will switch under turnout address=1*4+1=5 , with the third party control centre, however, it will switch under turnout address=0*4+1=1.
This means that when changing from an existing third party DCC system in particular to the Z21, it can be that the previously familiar turnout addresses appear to be shifted by a value of 4 due to the different counting methods. If a turnout on the previous third party system was being controlled using turnout address 1, as shown in the example, on the Z21 it will be addressed under  turnout address 5.

It is also especially confusing if the address of a new, modern turnout decoder can be programmed via CV, and that decoder uses a "counting method from module 1" with no explanation.
To make it easier for our customers to switch over and use third party decoders, the Z21 Maintenance Tool has an option "DCC turnout-addressing +4". When this option is enabled, the Z21 "translates" the turnout address to the module address and port number to be compatible with the third party system. This means, for example, that the turnouts and signals continue to be used with the turnout addresses you're already using.

Lastly, it is worth pointing out that this issue only occurs in connection with DCC. With Motorola turnout decoders the turnout address and track signal generation is unique.

5. Technical details

5.1. Can I set the output voltage on the track?

The output voltage can be set on the black Z21 between 12 and 24 V. However, the actual track voltage can only be a maximum of 1 V below the input voltage.

E.g. input voltage 20 V, set 18 V = track voltage 18 V

E.g. input voltage 20 V, set 24 V = track voltage 19 V 

E.g. input voltage 20 V, set 12 V = track voltage 12 V

On the white z21, however, the output voltage cannot be adjusted and is around 1 V below the input voltage. 

Please note that it is not possible to use a standard multimeter to measure the output voltage reliably. This applies both to the DCC signal and more specifically to the asymmetrical Motorola signal.

5.3. What is the power output of the Z21 on the output?

The power output on the track output is a product of the set track voltage and the maximum output. The direct voltage can be set on the black Z21. The maximum output current is 3 amperes. The output voltage for the model system can be increased accordingly by connecting a booster.

5.4. Does the Z21 have a short circuit and/or overload shutdown function?

Short circuits are always possible when operating a model railway. For safety reasons, and to avoid damage, the Z21 detects both short circuits and overloads, and cuts out at currents over 3 A. It is therefore better to limit the number of amperes per booster section.

5.5. Where is the power consumption of the Z21 measured?

Measurement is carried out on the main track output. The closed-circuit current is 0-10 mA, incidentally.

5.6. How many locomotive functions are possible with the Z21?

The Z21 can control up to 29 locomotive functions depending on the control device: Light (F0) and F1 to F28.

5.7. Can I control analogue locomotives using the Z21?

Analogue locomotives cannot be controlled using the Z21.

5.8. How many trains can the control centre control simultaneously?

The upper limit is 100 locomotives in firmware version V1.24. The corresponding prioritisation of the drive commands ensures a good response from the locomotives.

5.9. Which formats can be Z21 generate on the track?

The Z21 can generate DCC with 14, 28 and 128 speed steps as well as Motorola MMI and MMII.

5.10. Does the Z21 produce the “Railcom® cut-out”?

Yes, the Z21 can produce the RailCom®cut-out . However, the RailCom cut-out can also be deactivated in the app settings or in the Z21 Maintenance Tool should any problems arise with older decoders or boosters.

5.11. What is the maximum number of smartphones or tablets that can communicate with the Z21?

In practise, ten devices should not represent a problem. However, a theoretical upper limit is the maximum number of IP addresses on a sub-network, in other words 252.

5.12. Which protocol does the LAN interface use to communicate with the PC control software? Is this protocol open source or do I need a licence?

The Z21 LAN protocol has been available since the start of 2013 and can be found in the Downloads area. No licence is required to use it.

5.13. The supplied WLAN router has both LAN and WAN sockets. What is the difference?

The WAN socket can be used to connect the supplied router to your home network/internet connection. This means that the internet is available to you on your smartphone/tablet at all times. The Z21 must always remain connected to the LAN port of the WLAN router, namely the yellow sockets.

5.14. What are the dimensions of the Z21 and of the WLAN router?

Dimensions of the Z21: 207mm x 146mm x 37mm

Dimensions of the WLAN router: 174mm x 144mm x 30mm

5.15. Could it be that I am measuring other voltages on the main and programming tracks than the voltages I entered in the "Z21 settings" sub-menu?

It is not possible to measure the output voltage of the Z21 using a multimeter. The output voltage is a switched-mode alternating voltage. The Motorola signal (IDLE command!) is also asymmetrical. The digital decoder interprets this switched-mode alternating voltage and uses it to generate the operating voltage and the drive information for the locomotive. Normal multimeters are set up for sinusoidal voltages in the alternating voltage range. Incorrect values will result if they are used to measure other, non-sinusoidal voltages.

6. Other

6.1. How many boosters does my system need?

Our boosters supply approx. three amperes. The power consumption of your system can be estimated as follows: A stationary locomotive with light consumes approx. 100 mA, a moving loco between 300 and 600 mA. Mini light bulbs result in 30 mA, and an LED 10 mA. For digital couplings and smoke generators, add 100 mA per device, and for turnout decoders and turnout drives, 500 mA reserve.

6.2. Can I update all Zimo decoders using the Z21?

No, because some older Zimo decoders react sensitively to an interruption in the programming process. For this reason, the decoder update has been limited to the more recent models of decoder that are available from Roco and that handle updates reliably.
The decoder update is carried out using the Z21 Maintenance Tool. 

6.3. Can I use also the Z21 to edit ESU sounds and import them onto the ESU Sound Decoder?

With the Z21 it is not possible to import or edit sounds on the ESU LokSound Decoder. To import a new sound onto the ESU LokSound Decoder, you need the ESU LokProgrammer (software and hardware).

6.4. If the output is 3 A, why is only a small power pack supplied?

The "small" power pack is more than adequate as the systems are not generally operated continuously at 3 A. In addition, turnouts and other components are switched, leading to short-term current peaks. And these accessory items will certainly consume 0.5 A taken across the market. At 2.6 A of the power pack, the storage capacitors in the Z21 offers the full reserve for this, including across an extended period. In addition, the specified values of the power supply should be regarded "conservatively."

6.5. Is there anywhere I can take a look at the User Guide for the Z21?

Yes, you can download the User Guide for the Z21 from the Downloads area.

6.6. Is the Z21 also available without a WLAN router?

No, for various reasons the Z21 will only be available in combination with the WLAN router. A few of these reasons are outlined below:

  • The majority of our customers are not necessarily experienced with WLANs, and we want to make the product easy to set up using Plug&Play.
  • Only a small number of customers have a LAN port for their home router located close to their model railway.
  • Many customers have set up their model railway outside the secure WLAN range of their home router, meaning the integrated router ensures secure WLAN reception directly on the system. 

In contrast, the z21start is sold without a router in the starter sets. The corresponding, pre-configured WLAN router can be purchased separately as WLAN Package with activation code (10814)

6.7. Can I add the TP-Link router to a BT Smart Hub WLAN network as a repeater?

Unfortunately the "TP-Link" router supplied cannot be used as a repeater for an existing WLAN network. If this were an option, you would also need to reset the configuration with your smartphone/tablet!

6.8. How do I reset the WLAN router if need be?

On the rear of the TP-Link device on the far left is a recessed Reset button that can be pressed using the centre of a ballpoint pen. Instructions on how to use the router again can be found in the Z21 Router Configuration Guide in the downloads area.

6.9. How can I start using the WLAN router again after resetting it?

All the information on using the WLAN router again after resetting it can be found in the Z21 Router Configuration Guide in the Downloads area.

6.10. How do I change the password for the Z21 WLAN?

All the information on changing the password of the Z21 WLAN can be found in the Z21 Router Configuration Guide in the downloads area.

6.11. Can I change the IP address of the Z21 to make it the same as my home network?

To make the Z21 accessible for users unfamiliar with LAN/WLAN as well, we have decided to deliver a fully pre-configured product including pre-configured WLAN router. 

In some cases it may be desirable to use an existing home router. The IP address of the control centre can be switched over using the Z21 Maintenance Tool. We have not integrated this function into the Z21 app as the risk of accidental incorrect settings is too great. 

Modelleisenbahn GmbH cannot offer any support in the event of problems following a change to the IP address. Thank you for your understanding.

Tip: if you have changed your IP address and forgotten it, there is still the option to scan the network with the "Fing" app which will all devices present on the network with the IP and MAC addresses. The MAC address of the Z21 begins with "84:2B:BC".