LocoNet and LocoNet Cables


Two communications buses are inherent to every DCC system — the track bus and cab bus. The track bus is the means by which DCC instructions (in the form of data packets) are communicated from the DCC Booster(s) to decoders via the track. Specifications for the track bus are contained in the DCCStandards and Recommended Practices developed and issued by the National Model Railroad Association (NMRA), and can be accessed on the NMRA's web site at www.nmra.org. They apply to all DCC systems.The cab bus is the communications bus between the various components of a DCC system that are not part of the track bus. These include communications between throttles and the Command Station, Boosters, detection systems, signaling systems, radio/IR receivers, etc. There are no NMRA Standards or Recommended Practices for the cab bus, so each DCC manufacturer can choose the type of communications used for this purpose, and each of the major DCC manufacturers has done just this. Thus the various system cab buses are different so there is no interoperability between DCC systems at the cab bus level as there is at the track bus.Since most NTRAK clubs have adopted the Digitrax DCC system only the Digitrax cab bus, called LocoNet®, will be addressed. There will not be a comparison with other system cab buses either at the technical level or as to which is a better choice.The Digitrax cab bus, LocoNet, has both an electrical and a physical specification. The electrical specification and properties of LocoNet are defined and controlled by Digitrax; a technical description of LocoNet can be downloaded from the Digitrax web site. This document deals with the physical specification — the cable used to carry the LocoNet signals.For error free operation of the LocoNet in a DCC system care must be taken in the materials used, construction and interconnection of the various LocoNet cables that are used for the overall system. A fault in a LocoNet cable or cable plug, or how the network is connected together can create problems that can bring the entire system down, and be hard to trace.The intent of this document is to detail how to manufacture, test, configure, install and repair LocoNet cables. Sources for the various materials needed are provided, as well as detailed instructions. In each step of the way reasons are provided for doing things the recommended way. Many photos and illustrations aid in understanding the instructions.Care of LocoNet cables before, during, after and between train shows is also important as the RJ plugs can be easily damaged, or a wire in the cable broken. This topic is also covered, but requires someone to have the responsibility for the care and maintenance of the cables.Care up front in manufacturing and testing is well worth the effort. You can do the work well once and care for the LocoNet cables, or you can end up doing the work many times over to fix what was not done right the first time. 



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