Marklin Digital Systems Explained

By: Mark Mervine


There is a lot of information available for Märklin digital systems, but it takes some effort to find enough information to gain an overall understanding of what you need to put a complete system together. The goal of this paper is to explain the various components of the Märklin digital systems in a way that is easy to understand. In this document, I do not address the Delta system components that were Märklin’s lower cost digital system, but more limited in their capabilities.

Original Release:

The Märklin digital system was first released in the 1985-1986 timeframe. At the time, it was a revolutionary system based on a set of integrated circuits developed by Motorola. The design of the system uses digital signal ‘superimposed’ over track power. The system is designed to allow up to 80 trains to be operated simultaneously. Each digitally-capable engine has a decoder on board that can have its address set by a series of eight dip switches.

The initial Central Unit was the 6020. This unit was the ‘brains’ of the system, but there were no buttons, switches, or controllers, only connectors in the back for power and track feeds and side connectors for expanding the system. A Control 80 unit (6035) had to be purchased separately and connected to the right of the central station to allow for the control of trains. The Control 80, as its name implied, allowed for the control of up to 80 trains simultaneously. The system also allowed for the control of a single function on each locomotive. This function could be the headlight, interior train lights, telex couplers, etc. Up to ten Control 80 units could be added to the right of the central station.

Other components were also made available to expand the system. The Keyboard (6040) allows for the control of switches and signals. Each keyboard could control 16 switches or signals and up to 16 keyboards could be added to the left of the central station to control up to a total of 256 switches or signals. The Memory unit (6043) allowed for the programming of up to 24 route sequences of 20 components without the need for a computer. Up to 4 memory units could be connected to central unit. The Interface unit (6050 or 6051) allowed the system to be connected to a personal computer. Several programs have been developed by third parties to allow for computer control of the layout. It is also possible to write your own program using the Basic programming language.

The system is designed to be powered from a Digital Transformer unit (6001 110V or 6002 220V). Finally, a Booster unit (6015 and later 6017) was been made available for providing power to larger layouts. Each booster unit requires a separate transformer. Since a typical digital transformer can power 3-4 trains simultaneously, each booster unit added to the system allows for the simultaneous control of an additional 3-4 trains.

In 1988, the Control 80F was released. This added four additional function controls and was originally intended to allow control of cars with special features such as the Panorama Car with the moving waiter.

In 1989, the Central Control unit (6022) was released. This was sold with some starter sets and may have been available separately. The Central Control unit was a pretty interesting device in that it included a controller that allowed for control of up to four trains. The four trains had to have their decoders set for addresses 10, 20, 30, or 40, but the system was expandable. Control 80 units, keyboards, etc. could all be added to the 6022, just like the 6020. Another interesting aspect of the 6022 was that it included a ‘mini’ keyboard that allowed for the control of up to four switches or signals.

Additionally, the Central Control I (6023) was also released. It was virtually identical to the 6022 except that it also included a computer interface. This unit was also sold with some starter sets, but was definitely made available separately as well. From a value perspective, the 6023 was a most impressive offering. The only real limitation of the 6023 was that only 4 S88 feedback modules could be used with it.

For controlling devices such as turnouts, signals, and other devices the K83 (6083) and K84 (6084) decoders were available. For sensing train position for a memory or computer control, an S88 (6088) feedback module was made available.

Second Generation:

In 1994 Märklin released the second generation version of their digital system. This system was backwards compatible with the original system, but added some important features. First, direction indication was added so that arrow indicators on the Control 80F would show the direction of the train being controlled. Also, the four function additional function keys could now control additional locomotive functions.

The heart of the new digital system was the Control Unit (6021). The nice thing about this unit is that it combined the functionality of the Central Unit and the Control 80F all in one unit. All of the original components (except the 6020) could be re-used with the 6021. Along with the 6021, a new Interface unit (6051) was also released. This unit was functionally the same as the original 6050.

Third Generation:

Märklin is in the process of releasing their third generation digital system based on MFX technology. MFX technology allows for up to sixteen locomotive functions and two way data communication. The major components of this new system are the Mobile Station and Central Station.

The Mobile Station has been available for some time and is sold with the new starter sets. Up to ten locomotives can be stored in the Mobile Station (MFX locomotives will register automatically), so that you no longer need to remember their digital address. Additionally, two Mobile Stations may be used together to have two throttles. The Mobile Station allows for the use of nine locomotive functions, but does not have the ability to control turnouts or other digital accessories. For a small layout, with manual control of switches, use the Mobile Station is a very nice option.

The new Central Station was released last year. Unfortunately, the development of this system was done in partnership with ESU and the partnership has fallen apart. Thus, the add on components (such as boosters) have not yet been released.

New to Digital?

If you are new to Märklin and are interested in digital control, there are several different approaches that you could take. With the impending release of the new third generation system, the older components have been discontinued. The 6021 control unit is still pretty available, but the other units are getting difficult to find.

The first and second generation systems are based on fairly old technology by today’s standards but, they have the advantage of being simple to operate and fairly rugged. Although it takes some effort, a complete system can still be put together from the second hand market. The best way to start would probably be to obtain a Central Control (6021) unit and skip the 6020. However, since most locomotives only have a single function, a 6022 or 6023 may be a good starting point if found at a ‘reasonable’ price. The other unit that is probably essential is the Keyboard unit (6040) to allow for the control of switches and signals. You may also want to add a Control 80F (6036) as a second speed controller. An older Control 80 (6035) will also work fine with the 6021, but it will only control a single function and not indicate direction. Again, most locomotives only have a single function, so this is not really a limitation of a second throttle.

Another option would be to consider the purchase of an Intellibox. This system is made by Uhlenbrock and is designed to be fully compatible with the first and second generation Märklin digital systems. The initial purchase price of the Intellibox is high, but in combines the features of the 6021, 6036, 6040, 6043 and 6051 all in one unit. The keyboard and memory features are accessed via menus and most operators still prefer to have at least one Märklin keyboard. Like the 6020, 6021, 6022, and 6023, the Intellibox allows for expansion and the use of all Märklin 6035, 6036, 6040, and 6043 units. Additionally, an adapter is available for the Intellibox that allows the use of a 6021 as a 6036. Thus, if you have a 6021, and upgrade to an Intellibox, the 6021 can become a third throttle control. Uhlenbrock has also designed an adapter that allows the new mobile station to be connected and used as a third throttle. One additional feature of the Intellibox is that the serial port can be used to install software updates. This capability has allowed the Intellibox to keep up with new features. Whether or not Uhlenbrock will be able to add mfx capability to the Intellibox is one potential concern for the future.

A third option would be to use the new central station from Märklin. Although there will not initially be many locomotives available that can take advantage of the new features, as time goes by more will be available. Having seen the new central station in operation, it will take some getting used to. It has a large touch screen and is, essentially, a computer. Most of the features are accessed via menus and, in real time layout operations, the simplicity of the ‘older’ keyboards and controllers will probably still have an advantage. After a lot of feedback from customers, Märklin has decided to develop interfaces that will allow the use of the older digital units with the new central station. When these will be available and how well they will work is yet to be seen. Also, the Ethernet port for computer control has not been activated.

Finally, the forth option would be ECoS from ESU. This system is very much like an improved central station, but without support for MFX. It does, however, have a built in interface for the S88 and allows continued use of older Märklin or Uhlenbrock digital components via the build in ECoSniffer port. It is due to be released in the US in late 2006 and may turn out to be serious competition for Märklin and Uhlenbrock. Like the central station, the Ethernet port for computer control has not yet been activated on ECoS.


Originally, the Märklin digital units were very expensive and it would cost well over $1000 to put together a basic system. Fortunately, the system was manufactured very well and it is still possible to find enough units on the second hand market to put together a complete system. Lately, the cost of a second hand 6021 central control has dropped to around $100. Although the digital transformer (6001 or 6002) were intended to be used with the digital system, the 32VA transformer sold with starter sets does a good job of running 2 or 3 trains. The control 80F (6036) still goes for almost $200, but you may be able to find an older control 80 (6035) for approximately $80. If you have an engine that has more than one function, just make sure that you use the 6021 to control it and use the control 80 to control engines with only one function.

As mentioned above, you probably want to have at least one keyboard unit (6040) to control switches and signals. These are harder to find and have been selling for about $200 on the used market. There are very few memory units (6043) available on the used market. These seem to be selling for between $150-200. Finally, the interface units seem to be the hardest to find and go for about $200.

Therefore, if you want to put together a simple (yet complete) digital system for a small to medium size layout to run 3 to 4 trains, you will need the following:

Transformer (at least 32VA) $50-100

Control Unit (6021) $100

Control 80 (6035) $80

Total $230-280

If you only have engines with a single function, you could use one of the original generation systems, such as the 6022 or 6023 and save a lot of $$$ (limited to operating 4 trains without a control 80):

Transformer (at least 32VA) $50-100

Control Unit (6022 or 6023) $80

Total $130-160

If you also want to add switches and/or signals and computer control:

Transformer (at least 32VA) $50-100

Control Unit (6021) $100

Control 80 (6035) $80

Keyboard $200

Interface $200

Total $630-680

As previously mentioned, an alternative would be to purchase an Intellibox. This would be especially true, if you want to add computer control:

Transformer (at least 32VA) $50-100

Intellibox $500*

Keyboard $200

Total $750-800

*estimated new selling price, other prices are estimated second hand prices

Typical Digital System Configuration:

Shown below is a typical digital system configuration for a small to medium size layout:

image008 image006 image002 image004



In this configuration, simultaneous operation of 3-4 trains and a small number of switches and signals will be possible. Simultaneous operation of more than 3-4 trains will require the addition of a second transformer and booster unit.