The BiDi(RailCom) Display is a device developed by Lenz in Europe that interprets RailCom signals (called BiDi or BiDirectional in the NMRA standard) and displays the address of the vehicle. RailCom is a registered trademark of Lenz in Europe.
RailCom is a registered trademark of Lenz AG in Europe. This device can detect the address of a vehicle and show the address number on the display by placing this device between the command station and the rail line.
Please note that Transponding, a similar system from Digitrax, is not supported at all. For more information about Transponding, please contact Digitracs.
BiDi Display is developed in collaboration with Nagoden.
RailCom is a key technology for automated driving. RailComDisplay is effective for checking the operation of decoders and command stations that support RailCom. It is suitable for those who are interested in RailCom and plan to install RailCom systems in the future.
- It is suitable for those who are interested in RailCom and those who are planning to install RailCom system.
- Open source and open hardware, so you can play with it in various ways.
- The size of the board is compatible with Akizuki Denshi's C board, so you can easily get Akizuki Denshi's acrylic board case.
- Based on Arduino UNO, you can modify the circuit and software by yourself and enjoy the electronic construction with RailCom.
We have prepared a brief document about RailCom in PDF format. If you are interested, please take a look.
Introduction to RailCom and how it communicates (PDF 1MB, rev 1.2)
How to use
- Depending on the decoder, CV settings may be required; RailCom is enabled by default for LokSound5.
- The J and K side should be the command station and the J1 and K1 side should be the line. However, it will also work in reverse.
- The RailCom Cutout function must be enabled on the command station, otherwise the command station which does not support RailCom will not work.
- Please set the 3rd bit of CV29 of decoder to ON (Railcom enabled).
- It is possible to read from only one decoder at a time. If two or more Railcom-compatible decoders are in the same section, they cannot be recognized.
- It can be used by connecting them in parallel. In case of series, it may not work.
If you use DSair2, please enable Enable RailComCutOut. The screen display may be strange and you may need to toggle it once.
Gap indicates that there is no connection between the tracks. 24-816 Insulated Joiner is useful when using KATO's Unitrack tracks.
On the left is a normal joiner. On the right is an insulating joiner.
This is the situation with the joiner attached to the HO unitrack track.
The back side.
CV29 bit3 must be ON; if it is OFF, RailcomDisplay will not work at all.
|CV No.||Setting the CV value||Remarks|
|CV28||When Bit0 is ON, address notification is enabled \ When Bit1 is ON, data delivery such as speed is enabled \ When Bit2 is ON, response to command is enabled||It is recommended to set Bit0 to 1 (CV28=1).|
Command station corresponding to RailCom
A command station that supports the RailCom Cutout function is required. \fnDroid Sans Fallback Please note that KATO (D101, D102), Digitrax, Bachmann, NGDCC (Red Box) and old DesktopStation products that are widely used in Japan are not supported.
- DesktopStation DSair2
- Roco Z21
- ESU ECoS2
- Digikeijs DR5000
Decoders compatible with RailCom
Mainly European decoders are supported. Please note that Japanese and American decoders are not supported. Be sure to set CV29 Bit3 to ON.
LokSound4 and LokSound5 used in Open Sound Data are compatible with RailCom as standard.
|Germany||ESU||LokSound series, LokPilot series|
|Germany||Lenz||SILVER mini+, Standerd V2, 10321-01 SILVER21+|
It seems that TRIX vehicles do not support RailCom.
Decoders that do not support RailCom
The following are not decoders that support RailCom, so their addresses are not displayed in RailcomDisplay. The following decoders are not RailCom-compatible decoders, and therefore do not display addresses in RailcomDisplay. However, they are decoders that have been tested and confirmed to cause no particular problems when communicating via RailCom.
There is no evidence that RailCom communication will cause the decoder to run out of control or go wrong. There is no evidence that the decoder will run out of control or go wrong when RailCom communication is used. However, there is also no evidence that the decoder will never run out of control due to the fact that the decoder performs instantaneous low and high several times a second, which is not the original function of DCC. Therefore, we are gathering information and preparing an environment to use RailCom in a stable manner.
|DesktopStation||DSservo (possible to countermeasure problems with capacitor enhancement modification),DSturnout,|
|Marklin||6080, Fx Decoder,|
DSturnout, | |SOUNDTRAXX | |Marklin | 6080, Fx Decoder,| |Nagoden | |QSI Fx Decoder,| |Nucky Decoder,|QSI,|Tenshodo,|Kantum,|
|Nucky||FPM Decoder, One-Coin Decoder Series|
Decoders with unstable behavior (jerky running):
Digitrax DN163k4a, EM13
Schematics and Artwork
|Part No.||Specifications||Akizuki Part No.||Remarks|
|7SEG|| 0.56“ 4-digit 7SEG|
OSL40562\ Anode Common
|CN1,CN3||Euro connector EG3.81 2pin|
The firmware is compiled and written in the Arduino IDE. It is distributed as source code. If you find any bugs, please report them to us.
The RailComDisplay board is a microcontroller bootloader, which is an Arduino UNO compatible board. However, because RailCom communication occupies only one hardware UART, it cannot be written by upload (USB UART) which is usually used. Therefore, you need to write the sketch directly to the flash memory inside the microcontroller (write via the writing device).
CN4 ICSP is fully pin-compatible with the ISP pin of AVR (Arduino UNO), so please solder 2×3 pin headers or use a pogo pin writing jig to enable writing according to your own environment.
You can use the ICSP writer based on Arduino Nano or UNO to write. For the board setup, select Arduino UNO and write using “Write via Writer”. The writing device supports only “Arduino as ISP”.
ICSP writing is a common method in electronic engineering. If you search for “Arduino ISP writing” or “ICSP AVR”, you will find a lot of information.
This device is under development as of January 2021 and is intended for advanced DCC users. It is intended for those who have a grasp of controllers and decoders that support RailCom.
This will be done at Digital Model Railroad Forum.
Frequently Asked Questions
Are Digitrax products supported?
No, they are not supported. Digitrax has developed its own system called Transponding, which is included in the decoder. If you want to use BiDi Display, we recommend you to migrate to European DCC decoders such as ESU, Lenz or ZIMO.
It doesn't work!
Both the command station and the decoder must be supported. Also, you need to enable the BiDi feature for it to work. To check, when you put BiDi Display, if ”-“ is blinking, BiDi signal is not coming. If the ”-“ is always lit, the command station is sending BiDi signal to the decoder.
On the decoder side, bit3 of CV29 must be turned on to use the BiDi function.
Also, depending on the decoder, CV28 must be set to 1 to work properly (e.g. Kuehn's decoder).
Decoder has run out of control
The BiDi mechanism is such that it does not affect the operation of the decoder. We would appreciate it if you could inform DesktopStation of the decoder that causes the trouble. If you have a decoder that is giving you trouble, please let us know in detail the conditions under which it occurs.
The address is not recognized even though everything is checked
In DSair2, before R3, BiDi signal is not output immediately after power-on, but after R3.1, BiDi CutOut signal is output by default.
When the RailcomDisplay bar is blinking, there is no BiDi signal coming.
The next thing is, when there are only idle packets, the address is also not recognized. Try giving a speed or function to the appropriate address, whatever it is. It should be able to recognize the address.
Can it be used for automatic operation?
BiDi Display itself can not be used for automatic driving. We are planning to develop a detector for automatic driving with Nagoden, DCC Electronic Engineering Coalition, and other collaborators.
Sometimes it does not recognize
BiDi is basically designed to recognize a running vehicle. It can recognize a stopped vehicle, but it may be difficult to recognize it because of poor contact or limited communication data.
It may be possible to make it easier to respond by deliberately giving the vehicle an appropriate speed.
Command station is cut off by overcurrent
The BiDi Display is equipped with a capacitor, which causes a momentary inrush current when it is powered on, which should be within the acceptable range for one unit. However, if this is not possible, it is necessary to modify the board by installing a resistor (10-100Ω) inside the power supply circuit.
How do I set up BiDi (RailCom) in LokSound?
Which command stations have been tested?
The following are available, updated January 24, 2021.
Which decoders have been confirmed to work?
The following are as of January 24, 2021.
|Lenz||Silver + mini, Standard V2|
|ESU||LokSound5 series, RailCom Transmitter Unit|
|ZIMO||OEM for Fleishmann,|
Reference sites and literature
RailCom's patents, licenses, etc.
RailCom is a trademark of Lenz AG of Germany in the EU; as of 2021, no trademark registrations outside the EU are invalid or have been filed. \fnDroid Sans Fallback The patent related to RailCom (EP1380326), which was filed and valid in the EU and the US, has been abandoned gradually since July 2016 and can be used freely since June 2017. In Japan, there was originally no patent application filed for RailCom. Now, the RailCom technology described in the patent can be freely used without the need to conclude a license worldwide.
EP1380326, "Method and device for digitally controlling electrical apparatus of a model train system". Filing date: 14/01/2004 Invalidation date in Germany: 02/01/2017 (invalid due to non-payment of patent maintenance fees) Date of invalidation in the UK (31/05/2017), the patent is invalid.
However, this does not apply to RailComPlus (RailCom+), which was jointly developed by ESU and Lenz, although the relevant patents and other details are unknown. This page does not contain any technical conflicts regarding RailComPlus, and no features or technologies related to RailComPlus are used by DesktopStation or its affiliated organizations.
|Trademark||Trademark number||Expiration date|
|RAILCOMPLUS||DE503020110069573||February 28, 2031|
|RAILCOMPLUS||WO500000001095692||July 20, 2021|
|RailCom||DE30116303||March 31, 2021|
The web contains many points about RailCom's license, but almost all of them were written before 2016. Almost all of them were written before 2016, because it was not added that the patent was invalidated in stages in 2016 (the history is available from the European Patent Office), and as of 2021, RailCom's license is nonsense.
When contacting DesktopStation about RailCom's patents and licenses, please be aware of the correct IP and clearly point out the laws and regulations on which they are based.