RailCom Technical
Information

RailCom® - Advanced DCC control for the advanced Model Railroad Control

RailCOM is the  DCC industry's first standard bi-directional protocol for Locomotive and Accessory decoders.  In keeping with the spirit of DCC Lenz GmbH, presented RailCom at the Spring 2000 NMRA DCC Working Group meeting.  Since that meeting we have enhanced the capabilities of RailCom significantly and have been working closely with the NMRA DCC Working Group to develop  full bi-directional communication for DCC decoders.  We worked closely with the NMRA to evolve this proposal and in the summer of 2003 the NMRA approved the initial versions of RP-9.3.1 and RP-9.3.2.  Since then we have worked to further enhance and improve these protocols and in the spring of 2004 demonstrated to the WG the first working prototypes of the enhanced approach.  All in attendance were impressed with the performance of the enhancements.

RailCom introduces a whole new generation of capabilities for DCC by providing for the first time the ability of a DCC decoder to communicate information back to the command station. Such information can potentially include such items as advanced acknowledgement, current speed and direction,  real-time load, fuel and water used, absolute position reporting and turnout location.

RailCom works on the concept that a decoder is sent a packet requesting information and the decoder then responds by encoding information that is transmitted during a predefined zone in the following packet.

There are several key concepts that RailCom enables.  The first is that by acknowledging a packet the command station knows that the packet was successfully received and thus does not need to be sent again.  This can significantly reduce the packet bandwidth requirements for DCC thereby allowing more advanced communications to take place. This concept is already specified in the existing NMRA RPs and with RailCom all of these features can now be realized.

But there is much more to the RailCom concept. Rather than just sending a simple acknowledgement, we can now send  a lot of additional information such as the decoders address, current speed and actual load.  This allows transmission of much more than just a simple yes/no answer.  For example, we can now send a speed packet to the decoder and receive back the actual speed that the locomotive is currently traveling. This allows the command station to display the actual speed the locomotive is traveling rather than using an artificial speed step.  RailCom also allows the command station to understand the load that the train is pulling and allows it to adjust the operation accordingly. The end result is a much more realistic control at the handheld, as for the first time the locomotive engineer will be able to get the experience of operating a real train. 

Why did we wait so long to release RailCom products?   The reason is that we wish to move forward in a controlled and orderly fashion.   We have worked with the entire NMRA DCC industry to provide reference designs which will allow the free adoption of this new technology by all.  Now with the completion of this effort we will release our first products shortly.  While RailCom is very powerful, there are limits to the technology and therefore we needed to work closely with the community so that we could choose carefully which information we desire to transmit back.  It is important that this information be standard so that one decoder manufacturer does not decide to transmit one type of information which another's interprets differently.  The future continues to be bright for the evolution of DCC.

 Copyright Lenz Agency and Lenz GmbH 2008