Marklin Digital Basics

Märklin Digital Basics

Introduction

Since their introduction in the 1980's, digital control systems have evolved into a sophisticated technology that has become an integral part of model railroading. This technology has greatly simplified the construction and operation of model railroads, while also providing previously undreamt of operating possibilities and prototypical realism. These systems offer an exceptional value for newcomers to the hobby, and support the unlimited expansion potential desired by experienced model railroaders.

Before digital control systems, even a small layout with a few turnouts and accessories required extensive wiring. Separate power blocks with their own transformers were necessary to control multiple trains, while rows of toggle switches and bundles of wires activated turnouts and accessories. Digital systems replace all of this with a modern digital controller and a single pair of wires. Several locomotives, turnouts, and signals can now be operated within the same digital circuit. Instead of discrete wires, these components are individually controlled by digital commands, which are embedded into the electrical voltage that powers them.

This same technology simplifies the way layouts are operated as well. Because the system is digital, it opens a new realm of possibilities based on computer control. Complex layout operations that had once required much operator intervention and were somewhat unsafe as a result, can now be activated by the press of a button or automatically by the trains themselves. This type of control affords the same safety measures and time scheduling of the real railroad to its model.

Digital technology has also made it possible for scale models to more closely reproduce the true impression of their prototype. Onboard digital sound systems have elevated model railroading to new heights of realism. Now you can not only watch the motion of a steam engine's valve gear, but also hear the chuffing of steam exhausting from its cylinders. Realistic horns, whistles, bells, squealing brakes, coal shoveling sounds, and diesel engine noises are just some of the many features available on modern digital locomotives.

Whether you are new to the world of model railroading or a seasoned expert, digital control is an aspect of the hobby that you will benefit from greatly. The ease of setup and use makes a digital system terrific for beginners, and its ability to be expanded quickly and economically makes it well-suited to experienced users as well. With all of the added possibilities and enjoyment that a digital control system provides, it is no surprise that they have become such an important part of model railroading.

Digital System Operation

A digital model railroad consists of the operator control system and numerous digital decoders installed on the layout. The control system contains locomotive throttles, buttons for controlling accessories, and possibly even a computer. The decoders come in a variety of forms, depending on their application. The most common decoders are those used to control accessories such as turnouts and signals, and those built-in to digital locomotives.

The communication between the control system and these decoders occurs using digitally-encoded signals. These signals represent a series of digital address and command sets that are issued by the control system to all of the decoders on the layout. So that only the intended decoder will respond to the commands that are sent for it, each decoder is assigned a unique digital address. In this way, all of the decoders receive the same "broadcasted" set of digital signals, but only the decoder that is "tuned" to the right "channel" will respond to the commands for that address.

The digital signal is transmitted directly through the track, as a modulation of the voltage that powers the locomotives and accessories on the layout. Here, the commands can be used by locomotive decoders as well as any accessory decoders connected to the track. This efficient method of control and signal transmission results in extremely simple wiring, and eliminates much of the clutter and complexity previously required even by a small layout.

Control System Components

The digital control system requires certain fundamental components to perform its basic functions, these are: the central unit, booster, locomotive controller, and accessory controller. More elaborate control systems may also contain some type of route controller and/or a computer interface to facilitate advanced features such as layout automation. These individual components are available as separate add-on devices, but are also found in combination as multi-function devices called control units. The control unit is the starting point of any digital control system. Each system can contain only one control unit, since this device also houses the system's central unit.

The most important part of any control system is the central unit. It is the core of the entire control system. The central unit oversees and collects all of the commands that are issued by the various accessory, locomotive, and route controllers in the system as well as the computer interface. It is responsible for converting these operator commands into the digital commands that control all of the decoders on the layout. The central unit also determines the command format, sometimes referred to as the protocol or language, that is used to control the decoders. Most central units can generate only one digital command format: DCC, Motorola, or Selectrix. A multi-protocol central unit, such as that of the Intellibox, can generate all of these formats simultaneously. The command format of the decoders used on the layout must match the central unit.

Once the digital commands have been generated by the central unit, it is the role of the booster to amplify them with power and transmit them directly to the track. Most boosters also continuously monitor the electrical status of the layout that they power. If a short-circuit occurs or they become otherwise overloaded, they will automatically disable their output. The control system immediately notifies the operator of these events on the displays of the controllers. While most digital control units contain their own booster to power the track, larger layouts usually require separate add-on boosters to supply more digital power to the layout.

An operator issues these commands to digital locomotives on the layout using a locomotive controller. A typical locomotive controller has buttons for selecting the locomotive address, and a throttle and a reversing switch for controlling the locomotive. There is also usually a group of buttons for accessing auxiliary operating functions. These keys control the directional lighting, any additional lights, a smoke unit, TELEX couplers, and special sound effects of digital locomotives. A digital control unit will contain at least one locomotive controller, and can be expanded with separate add-on controllers so that more than one locomotive can be directly controlled at a time.

To control turnouts, signals, uncoupling tracks, lighting, or any other accessory connected to a digital decoder, an accessory controller is required. Most accessory controllers consist of a large keyboard containing several rows of red and green key pairs that are assigned to control a specific accessory decoder channel. Some control units, such as the Intellibox, include an accessory controller, but most do not. They are usually found as an add-on component to expand the control system.

Layout operations that require several steps on an accessory controller can be simplified by automating them with a route controller. A route controller memorizes the accessory commands as a route that can be quickly and safely activated with a single button. Route controllers are similar in appearance to accessory controllers, except that their keys activate entire routes instead of individual accessories. Route controllers also provide the added advantage of being controlled automatically by special digital decoders called feedback modules. For layouts without computer control, a route controller provides a very easy way to automate many multi-step operations.

To greatly improve and simplify the operation of larger, more complex layouts, a computer interface for computer control provides an excellent solution. Together with digital layout feedback, the interface allows a computer to monitor and control both the locomotive and accessory functions of the entire layout. This feature can be used to safely automate train movements with secure route control and for the creation of realistic train schedules - the operating possibilities are virtually endless. Moreover, flexible control software allows the operator to reconfigure the operations of the layout and the user interface without any rewiring or additional new equipment.

Digital Decoders

In order for the control system to communicate with locomotives and accessories on the layout, each of them must be equipped with a digital decoder. There are several types of decoders, intended for different purposes and applications. The main types are: locomotive, function, accessory, and feedback decoders. Sometimes these decoders are stand alone units, as is the case with most accessory and feedback decoders. And sometimes they are a custom electronics board installed in a locomotive, underneath a turnout, or inside a coach or other accessory.

Beginning in the early 1990's, most Märklin HO 3-rail locomotives are factory-equipped with some type of digital locomotive decoder. Many variations of digital decoders have been produced over the years for the different Märklin digital families including Delta, Digital, and mfx. However, these decoders can all operate within the various system families since they are all capable of understanding the same basic commands of the Märklin Motorola format. The simplest decoders, produced for the Delta digital system, allow the operator only to address the locomotive and change its speed and direction using a locomotive controller. Later designs of locomotive decoders, for the Digital and mfx digital systems, include many additional features. Electronic load control, adjustable running characteristics, as well as several special auxiliary functions such as sound effects, lighting functions, operating pantographs, etc. are accessible on these advanced decoders.

Before locomotive decoders contained these built-in extended functions, separate function decoders were used for this purpose. A function decoder can control locomotive lights, turn a smoke unit on or off, or control TELEX remote couplers, for example. Function decoders are now most commonly used in coach consists to control train lighting and any special sound effects. These decoders are controlled from the function keys of locomotive controller in the same way as a locomotive's extended functions.

To control accessories digitally, there are two general types of accessory decoders: momentary and continuous. Momentary accessory decoders supply short pulses of current to accessories such as turnouts, signals, uncoupling tracks, and relays. All of these accessories contain coils or solenoids that convert this short electrical pulse into a magnetic field that operates the accessory. Continuous accessory decoders supply a set of switch contacts that can be used to turn power on or off to track circuits, motors, and lighting circuits. These decoders can be thought of as a digital version of a standard relay. Most accessory decoders have multiple channels, so that they can control more than one accessory. There are also some special accessory decoders like those for Märklin C-Track turnouts, which have only one output and are intended solely for this purpose.

To be able to control all of the different decoders on the layout automatically, the control system can use information from the layout that is supplied by digital feedback decoders. Feedback decoders, also called feedback modules, monitor the status of the layout through their many input contacts that are installed around the layout. These contacts are most commonly used to sense the presence of trains. They tell the feedback modules which tracks are occupied by trains and which are not. This information can then be used to automatically activate or deactivate many layout functions through the application of a route controller or a computer. Digital feedback is very useful in the creation of automatic digital block operations and station entrance and exit routes.

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