Digital Command Control

The DCC protocol is defined by the Digital Command Control Working group of the US National Model Railroad Association (NMRA).

A digital command control system was developed (under contract by Lenz Elektronik GmbH of Germany) in the 1980s for two German model railway manufacturers, Märklin and Arnold.

In 2006 Lenz, together with Kühn, Zimo and Tams, started development of an extension to the DCC protocol to allow a feedback channel from decoders to the command station.

This feedback channel can typically be used to signal which train occupies a certain section, but as well to inform the command station of the actual speed of an engine.

Layout command control (LCC), previously known as "NMRANet", is a standard introduced in 2015 designed to relieve congestion on the DCC communication bus[6].

Increasing use of stationary decoders to achieve automation or animation has resulted in a large amount of packets causing congestion on the DCC bus.

For portable layouts this can greatly reduce the number of inter-board connections - only the digital signal and any accessory power supplies need cross baseboard joins.

There are two main European alternatives: Selectrix, an open Normen Europäischer Modellbahnen (NEM) standard, and the Märklin Digital proprietary system.

The US Rail-Lynx system provides power with a fixed voltage to the rails while commands are sent digitally using infrared light.

Several major manufacturers (including Märklin, Fleischmann, Roco, Hornby and Bachmann), have entered the DCC market alongside makers which specialize in it (including Lenz, Digitrax, ESU, ZIMO, Kühn, Tams, NCE, Digikeijs, and CVP Products, Sound Traxx, Train Control Systems and ZTC).