Support - RailCom®

From Train Control Systems Documentation
Jump to navigation Jump to search


RailCom is a bi-directional data communications technology found in The NMRA Standards & Recommended Practices 9.3.1 and 9.3.2 (currently under revision). RailCom enables bi-directional communication between the command station and decoders, unlike in traditional DCC where the communication is done exclusively in one direction (from the Command Station to the Decoder). The inclusion of RailCom opens up significant opportunities for future features and expansion. For example, the use of RailCom allows for real-time read-back of CVs while programming on the mainline. In traditional DCC, you would only be able to write to a CV, whereas with RailCom, writing and reading on the mainline are both possible.

Some other possibilities such as live feedback on a throttle for fuel/water level, temperature, and many other statistics are also unlocked with RailCom technology. Block detection becomes more integrated with RailCom as well, including the possibility of knowing who is occupying a block, rather than just knowing a block is occupied. This data could be used further to aide in automation setups and macros. A fleet of rolling stock could also be equipped with basic RailCom decoders to keep track of cars in yards or trains. The potential applications for RailCom are still being explored, and is an untapped wealth of possibilities!

RailCom is a highly-responsive system as well, allowing up to ~126 individual operations per second (depending on the available DCC bandwidth) at a bit-rate of 250Kbps by introducing a very brief interruption to the DCC track power. During this interruption, the RailCom detector on the Command Station will send or receive information to and from the decoder.

!!! IMPORTANT !!! "RailCom®" and "RailCom+" are not the same thing! RailCom® is a registered trademark of Lenz Elektronik GmbH and is notated and standardized in NMRA RP 9.3.1 and 9.3.2. This specification has been updated and continues to be updated through RailCommunity RCN-217. RailCom+ is an expanded version or RailCom which was modified and expanded upon by ESU (Electronic Solutions Ulm GmbH & Co.). The expanded featureset created by ESU is not available in any published documentation or standards. As such, TCS is not capable of developing our products to incorporate these unpublished features. Similarly, TCS cannot guarantee that all features of an ESU decoder featuring RailCom+ will operate correctly on a TCS command station with RailCom such as the CS-105.


In order to make use of RailCom, the following requirements have to be met:

  • The Command Station must provide a RailCom cutout and have a way to handle RailCom communication traffic.
  • RailCom Cutout must be enabled. You can find this in the CS-105 settings - DCC System Settings > Advanced > RailCom Cutout > Enabled.
    • If you are using a RailCom-enabled booster such the B-106, the RailCom data transmission over LCC must be enabled - DCC System Settings > Advanced > Drive LCC Boosters > Enabled must be set (as opposed to Enabled with no RailCom)
  • The decoder must support RailCom.
    • Supporting hardware is physically on the decoder (Check your decoder literature or refer to the chart below to see which TCS decoders support RailCom.)
    • RailCom enabled in CV 29 (see below)
  • RailCom- addressed feedback must be enabled in the decoder. CV 28 bit 2 must be set. (Typical values are CV 28=3 or CV 28=131) If you’re unsure, you can place the locomotive on the Programming Track to read the value of CV 28. A TCS UWT will show you which bits are set.
  • The locomotive must be…
    • on the track directly connected to the CS-105’s Mainline track output OR
    • on track powered by a RailCom-enabled booster connected to the LCC port (such as the B-106).

TCS Decoders with Supporting Hardware

The list below shows all decoder hardware types and Versions which support RailCom in hardware. Not all of the decoder hardware types on this list are still in production. IF A DECODER IS NOT LISTED BELOW, IT DOES NOT AND HAS NEVER SUPPORTED RAILCOM. If a decoder has a specified version number specified (Min. SW Ver.), only decoders with that version and newer support RailCom. If no Version is specified, all decoders of that type have the capability of using RailCom, but the newer the version, the more likely they are to work. Non-sound decoder version 94 is the current production version (as of March 2023).

RailCom is a continuously-evolving technology, so in some cases even a decoder with supporting hardware may not operate on a command station using the latest RailCom spec due to incompatibility issues. If you believe you are experiencing this particular issue, please contact our technical support staff to see how we can help you get up and running with TCS decoders and RailCom.

TCS Decoders With RailCom®
Decoder Name Scale ID (CV 249) Min. SW Ver.
DP5 HO 3
A4X HO 4
A6X HO 5
T4 HO 16
T6 HO 17
G8 HO 18
ALD4 N 19
AMD4 N 20
ASD4 N 21
K0D8 N (Varies)
K1D4 N 29
K1D4-NC N 30
K2D4 N 31
MP-15N N 38
LL8 HO 43
EU621 HO 44 SW Ver. 91
L1D4 N 45
K4D6 N 46 SW Ver. 92
AS6 HO 47
KAT22 HO 51
KAT24 HO 52
KAT26 HO 53
KAM4 HO 55 SW Ver. 93
T4-LED HO 54
KAM4 HO 55 SW Ver. 93
KAM4-LED HO 57 SW Ver. 93
T1-LED HO 58
K5D7 HO 59 SW Ver. 91
AZL4 Z 61
EU821 HO 65 SW Ver. 94
AZL1D4 Z 70
K8D6 N 71
DSV-1 OEM 181
DSV-2 OEM 182
OEM-21 OEM 190

Configuration Options

To enable RailCom on a TCS decoder, start by reading the value of CV 29. Compare the value to the chart shown below and reprogram as necessary. Once/If RailCom is enabled in CV 29, you may also need to set up CV 28 to allow for proper communications traffic flow. See the description and table below for more info and reprogram as necessary.

Support - RailCom®
Configuration Data #1
Range of Values0-255
Accepted Values0-255
Default Value6 (Varies)

NMRA CV 29 - Configuration Data #1

This CV is used to set up or enable basic functions of your decoder such as direction, speed step modes, enable/disable DC operation, and select the active address type. See the table below for more information on the settings controlled by this CV.

To determine which functions are active, use the table below and combine the values of the functions you would like to have active, and program the sum into CV 29. Fun Fact: TCS also offers a Calculator Tool

CV 29 - Configuration Data #1
Bit Feature Description Default Value
0 "Forward" Direction Selection This setting can be used to invert the polarity of the motor when the decoder receives a "forward" direction command (in DCC mode only).

This setting offers a software-level fix if the decoder or motor has been wired backwards, instead of re-wiring the engine. Direction-sensitive functions, such as the motor AND directional headlights will be reversed so that they line up with the locomotive’s new forward direction.

Note: This setting stacks with other related settings such as the Consist Direction setup, allowing you to have double-negatives in your configuration.

1 Speed Step Mode
This setting selects the speed step mode used by the decoder. This setting is not affected by your command station's throttle setting.

When enabled, 128 speed step mode is active - the decoder will interpolate 128 speed step mode from 28 speed steps if your command station is not configured for 128 speed step mode.

ON 2
2 Analogue (DC) Operation If this setting is enabled, the decoder will operate when DC power is applied. If this setting is disabled, the decoder will not operate when DC power is applied.

The functionality of your decoder is based on your DC Mode Settings.

ON 4
3 Bi-Directional Communication (RailCom) This setting determines whether the decoder will send or receive information over RailCom. See Bi-Directional Communication Configuration for more details ON 8
4 Speed Curve Selection This setting will switch from using the 3-Point Speed Curve (CV 2, CV 5, and CV 6) when "OFF" to using the 28-Point Speed Curve (CV 67 through CV 94) when "ON"

(Note: Even with the this setting enabled, CV 2 will always be enabled for use to "boost" the low speed if necessary)

OFF 16
5 Address Type This setting switches the Address Type between 2-digit and 4-digit addressing. When this setting is enabled, the decoder will use a 4-digit "long" address. OFF 32
Support - RailCom®
RailCom Configuration
Range of Values0-255
Accepted Values0-255
Default Value7 (Varies)

NMRA CV 28 - Bi-Directional Communication Configuration (RailCom®)

This CV is used to configure decoder’s bi-directional communication characteristics when RailCom is enabled in CV 29.

If the decoder does not support a feature contained in this table, it shall not allow the corresponding bit to be set improperly. E.G. if a decoder does not support RailCom, this CV will read 0 and will not accept any values to be programmed to it. Additionally, the decoder should not allow you to enable a feature within the table below which is not supported.

Bit Feature Description Default Value Supported by TCS
0 Channel 1 If enabled, Channel 1 will broadcast the address. ON 1 YES
1 Channel 2 If enabled, Channel 2 will send and receive data and provide acknowledgements. ON 2 YES
2 Auto Channel 1 Automatically Turn off Channel 1 ON 4 YES
3 (Reserved) Not Used N/A 8
4 Programming Address 3L If this setting is enabled, programming Long Address 3 will be allowed. OFF 16
5 (Reserved) Not Used N/A 32
6 Current Limit If enabled, the higher current limit for RailCom will be enabled OFF 64
7 Automatic Login If enabled, allows automatic login (RCN-218 or RailComPlus®) OFF 128 (Under Devel.)

Note: The table above is based upon the RailCom Specification RCN-217 and RCN-225 as of 01-16-2023 and as such is potentially subject to change. Additionally, the last column in this table "supported by TCS" is only true for current production decoders which support RailCom, and may be untrue for specific decoders and/or decoder versions (CV 7, or CV 110/CV 111) designed using an older revision of RCN-217.


RailCom® Trademark Note

RailCom® is a registered trademark of Lenz Elektronik GmbH