It will certainly be usable with the current production items, but you will run into restrictions that will become very annoying. You have the original control unit which can only control one function - the headlight. You will not have any other functions available to you. If you only want to run the stock you already have then this controller will be fine.

You don't say how large your existing loco roster is, but all digital locos will all run with the current model controllers that are available.

If you are looking to purchase a range of new items then you will need to invest in one of the current range of control units (ms2 or cs3).

The ms2 is limited to 16 functions per item (there are other items other than locos that can be controlled by these controllers), which means that higher numbered functions on some of the latest items are not available to you. The ms2 is designed as an entry level controller, and will quite happily work with any items you already own.

The cs3 is the fully fledged controller available from Marklin. It can also connect to some of the items you already have (through suitable adapters) allowing you to use them. There are two models of this controller, and to use your existing items most easily I would suggest getting the more featured version, the CS3+ as to add the necessary additional items to the less featured one so you can use the items you already have will come to around the same price as the full featured one.

Feel free to expand the information on what you have and there are a number of people here who will be only too happy to help you.

Sorry for my English, but what do you mean by "I have stored the CS3+ UG ..."?

If you are interested to read and get more explanation about a digital railway I recommend the Märklin book "Controlling Digitally with the Central Station 3" to you, notably it is in English available.

https://www.maerklin.de/...s/details/article/03092/

I got this book in German and it tells most of a digital railroad, even it gives a compact overview of all digital devices from Märklin.

A more modern controller will be better, and it need not be from Märklin. Other manufacturers such as ESU and Uhlenbrock now also make controllers that can drive the older locomotive decoders and the more modern ones.

The old 6050 used a serial port, not a printer port (which was parallel).

Something the others have neglected to tell you is that you could swap / upgrade the 6020 / 6035 by replacing them with a 6021 controller.

The 6021 can address up to 80 MM locomotive addresses, plus can control 4 locomotive functions in addition to the normal headlight function. The 6021 will work with your 6040, 6050, 6083 and 6015 devices, and they can be readily purchased off ebay second hand.

Quite a few folks on this forum still happily run their layouts with a 6021. All Marklin locos up to this day support the MM protocol, and if you are happy with 4 functions per loco rather than up to 32 functions, then go for it.

Correct - this is another reason why I started to add the link of the system architecture always to my relevant posts. Another reason is the missing link to these files in the English Märklin website version. You only can get there through the German website. But who does know this?

Even the system architectures in the Märklin books 03092 and 03070 are not as precise as these PDF files on Märklin's homepage.

But caution!
In these PDF files with the system architecture an error occurs to the previous years digital control units 6021. The needed (and still at Märklin available) connect-6021 unit art# 60128
for the CAN bus has the article# 60128 and NOT 60182 as written in the PDF overview of the system architecture.