The märklin Digital System - Components Explained

Table of Contents

Preface - Obsolete Information!

Please note that the following text describes the decoders and controlling devices of the pre-mfx era, i. e. the märklin motorola system components. They are now superseded by the märklin mfx system.

Introduction - Digital Model Railway Control

Undoubtedly Märklin has played a leading role in the introduction and establishment of digital control in the model railway business. Its proprietary Märklin/Motorola system has successfully survived the competition of various systems. The dominant alternative is the DCC/NMRA system introduced by Lenz, which has been adopted by model railway manufacturers like Arnold, Roco, and recently, Fleischmann. Other proprietary systems seem to be dying out gradually, like Fleischmann's FMZ, ZIMO's system, and SelecTrix.

There is one principal problem with proprietary systems. They are the idea of one company which tries to hide any technical details to prevent competitors to copy their intellectual property. Märklin is no exception. The märklin digital system is also known as the märklin/motorola system, because the data protocol used for information transmission is based on ICs by Motorola which were designed for remote control applications. In fact, these Motorola ICs are still used in decoders for turnouts, for example.

In general, any digital control system consists of transmitter devices, which the user is operating; and receiver devices, which process the received commands into actions. The information is carried over the rails by encoding the information into a signal, i. e. an appropriately shaped voltage. This mapping of information into a signal (the protocol) makes the difference between the various systems.

The transmitter devices, in the case of märklin, comprise a transformer as power supply, a central unit, which generates the electrical signal for the rails, and a control 80, where loco commands can be entered. Central unit and control 80 were two separate devices but are nowadays combined as one device, called control unit. Furthermore there is a keyboard, where turnout commands can be entered, an interface, to allow connection to a computer, and other devices. If the power output of the control unit is not sufficient for the whole layout, it has to be partitioned into several sections. A transformer and a booster is required for each new section. Here in the case of the märklin system, the user's control panels only produce a märklin/motorola signal. Other control panels may produce other system signals, like the Intellibox (märklin/motorola, DCC, Selectrix), the TWINCENTER (FMZ, DCC, Selectrix), or the software-based DDL (märklin/motorola, DCC).

The receiver devices are called "decoders". There are loco decoders inside the locos on the rails, and stationary decoders with momentary outputs for turnouts and permanent switching outputs to switch lights, for example. Some decoders understand several protocols, and most loco decoders also support the "analog" mode. "Analog" means you turn up the trafo, and all locos on the track go faster, they directly follow the analog voltage on the track. In the digital mode, the loco decoders listen to the digital signal on the rails, and interprete those commands addressed to them and act accordingly. Such action can be driving the motor, switching front lights, or activating additional functions, like smoke units, additional illumination, or sound effects. Of the multi-protocol decoders some automatically decide to which protocol to listen, others need to be configured to fix their current mode.

Thanks to many curious and smart people, the Märklin digital system is no secret any more but piece by piece uncovered and explained. By now the data protocol of the Märklin/Motorola is documented, the circuit diagrams of Märklin's Delta and digital decoders are reverse engineered, the schematics of turnout and permanent device decoders are found, do-it-yourself instructions are available to build your own devices cheaper than the originals. Other companies offer equivalent devices and kits.


Since märklin digital has been brought to the market, märklin have developed various types of decoders. The following two pages focus on the decoders.

Control Unit

With control unit I mean the "console" you use to control your trains, and maybe other accessories. Note that any märklin control unit can be combined with any märklin decoder, e.g. a 6021 central control can control a DELTA loco, a 6604 delta control can control a 37xxx high performance digital loco.

Links and References

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last update: 2004-02-21; webmaster(at)