Digitrax Products and the

NMRA Digital Command Control Standard and Recommended Practices

As a company, one of Digitrax’ goals has always been to offer model railroaders a complete layout control solution that includes basic and advanced train control, detection, transponding, signaling and much more. To that end LocoNet was developed in order to offer Digitrax customers the best of all options available. The Digitrax System is compatible with the NMRA DCC Standards and Recommended Practices but is not limited to them in the features that can be offered. The NMRA's DCC Standards and Recommended Practices are just one small subset of Digitrax LocoNet's broader system capabilities.

The NMRA Standards and RPs define only a basic level of interoperability for DCC equipment. They do not address other control formats, like trinary, Trix & FMZ, that are useful to model railroaders around the world. The NMRA's Standards & RPs do not cover features that are implemented on the track without using the DCC signal nor do they cover the network (or bus) communications strategies that allow for multi-format operation. As technology continues to develop we expect to see more multi-format equipment like the DCS100 and more innovative implementations of technology, like signaling, detection and transponding, that are complimentary to DCC but not necessarily related to DCC.

What does the "DCC symbol" mean?

Companies that sell interoperable equipment compatible with the NMRA's DCC Standard often use the DCC logo to let customers know that they support basic DCC standardization by producing DCC compatible equipment.

This symbol is seen on many DCC compatible products because the NMRA DCC Standards and RP's do not cover all DCC compatible equipment and therefore not all DCC compatible equipment is eligible for a conformance seal. Basically, command stations and decoders are covered by the Standards and RP's. Throttles (or cabs), computer interfaces, boosters (or power stations), computer based programmers, cab busses, control busses, control networks, radio and infrared interfaces, block detection devices and signaling devices are not covered by NMRA Standards or RPs.

THIS SYMBOL IS NOT A CONFORMANCE SEAL AND IS NOT AN ENDORSEMENT BY THE NMRA!

What does the NMRA Conformance Seal mean?

It means just what it says. "This Product Conforms To All Applicable NMRA Standards." An NMRA Conformance Seal is NOT an endorsement by the NMRA. It is NOT a guarantee by the NMRA or by the manufacturer. It is merely a statement that a particular product conforms to a particular test set up and administered by NMRA volunteers to assess whether, in their opinion, the product conforms to a particular NMRA Standard. Interpretations of this statement vary widely depending on whom you ask for clarification.

The Real Issue is Interoperability

Interoperability means that you don’t have to worry about a single source system. It means competition in the marketplace so that you have more choices and better prices.

Many manufacturers in the DCC industry have produced NMRA DCC interoperable systems for several years without the NMRA conformance process. These manufacturers will continue to produce compatible products and will continue to work hard to ensure backward compatibility with existing DCC equipment when new products are brought to market. As manufacturers, we realize the importance of interoperability to you, our customers. But, in reality, there is no absolute guarantee of DCC interoperability. The NMRA’s DCC Standard and RP’s are loosely drawn in some areas and narrowly drawn in others. The standards and RP’s are open to interpretation and sometimes different engineers do come up with different interpretations of the same "standards" document.

You may have heard about (or seen on the net or on the DCC SIG) discussions and lists of DCC compatibility problems posted by various (sometimes partisan) individuals. Some of the issues listed are "legacy" issues with DCC equipment that was produced before the Standards and RP's had progressed to their current state. Other issues have to do with products produced based on variations in interpretation of the Standard & RP's. Because DCC has evolved over many years and is continuing to evolve today, compatibility problems can be expected to arise from time to time. Unfortunately, we have even seen some products with conformance seals that have interoperability problems, too! The good news for consumers is that most of the time DCC equipment is interoperable because the DCC manufacturers take the extra time to be sure that it is. And even when there is an interoperability problem, there is usually a workaround offered by the manufacturers to get you up and running again. All of the major DCC manufacturers really do offer excellent customer service and support.

Even though the NMRA issues Conformance Seals you will continue to see many products that are DCC "compatible" but not necessarily "conforming." Even though the NMRA may have "tested" certain products, and issued conformance warrants for those product samples tested, we have even seen that there is little control over the products that actually wind up on retailer's shelves.

The bottom line on NMRA compatibility/conformance is that it we really count on the DCC manufacturers to maintain DCC interoperability. Chances are that you will never experience any interoperability problem with your DCC equipment regardless of whether it is NMRA DCC compatible or conforming and if you do, the manufacturers, not the NMRA, are the ones who will take care of any problems you might encounter.

In 1996 Digitrax received a conformance seal for the DB100 Challenger Command Station (Challenger was retired after 5 years of production in July 1998). Based on our experience in obtaining the Challenger Conformance warrant, we chose not to submit any additional Digitrax products for testing at that time.

Since then we have worked privately with the highest levels of NMRA leadership by making them aware of some very serious concerns that we had regarding 1) the actual testing being performed, 2) the documentation of that testing, 3) the conflict of interest of certain individuals involved in the program, 4) the legalities involved in the whole process and 5) the need for guaranteed confidentiality during testing of new products.

In the two years following the issuance of the DB100 Challenger Command Station Conformance seal, we have continued to work with the NMRA and now the NMRA has addressed many of our concerns as follows:

The actual C&I tests being performed by NMRA volunteers were improved considerably. Also, the NMRA purchased the minimum amount of test equipment (an oscilloscope) that was needed to perform the testing. There is still a long way to go but great progress was made between 1996 & 1998. There is still a need for complete independent verification and documentation of the tests so that we can be certain that the tests that are being performed really test for conformance. We need to test the tests!
Conformance testing is much better documented in 1998 than it was in 1996. Again, much work remains to be done in this area. In order to perform proper testing, we feel that flow charts need to be done for every test to be performed. This will insure that we do not miss steps critical to adequate testing. Flow charts will also give manufacturers a clear "road map" to design for conformance and help ensure common interpretation of the Standards & RP's.
The NMRA addressed our conflict of interest concern by removing the Conformance and Inspection Chairman who was serving in 1996 and replacing him with a new C&I Chairman with no financial or other interest in any model railroad business. We felt that this was very important because it was unreasonable to ask us to submit our products for testing to someone who might be associated with one of our competitors.
The concern for the NMRA's potential for liability was raised by AJ & Zana Ireland as NMRA members, not as principals in Digitrax. Their past experience in the electronics industry, experience with other standards bodies and the litiguous nature of today's society made them uncomfortable with the NMRA's C&I program. The NMRA legal department feels that the NMRA has minimal legal exposure related to the C&I program.
The issue of strict confidentiality in testing was addressed by the NMRAs agreement to institute confidentiality measures for testing. The C&I testers and officials involved with submission of Digitrax products for testing also agreed to sign Digitrax' non disclosure agreement. We are pleased to say that these measures worked very well.

Because of these efforts we were encouraged that the NMRA was moving forward with making the Conformance and Inspection Program into something that will become valuable to members in the future. Every member of the NMRA should thank Bob Charles, Ron Gaines, John Nawn, Brain Barnt, Bruce Stockdale, Ken West and the many other NMRA volunteers who have worked so hard to revive the NMRA Standards Program and the C&I program.

Even though there is still work to be done in the DCC area for C&I testing to reach its full potential and in light of the progress made by the NMRA in addressing our concerns, we decided to submit the DB150 command station for testing in September 1998. We would like to thank Bruce Stockdale (DCC command station tester) and John Nawn (C&I Chairman) for their efforts in completing the DB150 testing.

In October 1998, the NMRA awarded a conformance seal to the DB150 command station (this is the command station used by the Genesis II and Empire Builder II Starter Sets).

All of this really leads to the questions: "What's next?" "Will Digitrax pursue conformance for any more of its products?" The answer is simple, Digitrax will continue to concentrate on building products that are compatible with the NMRA standard and that interoperate with other DCC compatible systems. We will continue to cooperate with the NMRA and its volunteers in their efforts to establish standards and RP’s that make sense for the hobby and are not overly restrictive or unfair to any manufacturer. We will not support any change to NMRA Standards or RPs that will adversely affect products made by any manufacturer that is currently in the field because we feel that this would also adversely affect model railroaders who own those products. Digitrax may submit future products for conformance when it makes sense to do so. This has been our company policy on conformance from the beginning and we do not forsee any need for a policy change in the near future.

With LocoNetâ , Digitrax customers have the best of both worlds. The Digitrax System is compatible with the NMRA DCC Standards and Recommended Practices but is not limited to them in the features that can be offered. This is because the NMRA's DCC Standards and Recommended Practices are just one small subset of Digitrax LocoNet's broader system capabilities.

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Updated 11-27-00