I’ve built a new app which transforms your iPhone or iPad into a retro-inspired model train controller for your Märklin CS2 or CS3, just for fun.

How did this happen?

Well, I needed a small app to test my new Swift CAN framework, which will be used in a future version of RailControl Pro. The app needed a keyboard, to type in an address for a loc or an accessory, and then a way to control speed, functions or states. Before I knew it, I ended up with something very similar to an old Märklin Control Unit.

This gave me an idea. As a kid from the eighties, for years I was dreaming of owning a Control Unit. I had no idea how it worked, I had just seen it in Märklin’s catalogue over and over again. It looked so cool. The modules, endless buttons, the speed knob, the colors. Everything basically. So what if I made my test app look like a Control Unit? How cool would that be? And what if I added a Keyboard?

Eventually, it got a bit out of hand: I bought a beat-up Control Unit and other modules for cheap, and discovered how these devices actually worked. Then I made sure my app matched that behavior (yes, even the L and F buttons). Several coding nights later, RailControl Unit was born.

Why release it?

I figured, maybe some people feel as nostalgic as I do about the early days of Märklin digital. So that’s why I’ve made this app available for you too. Of course, the functionality of those old Märklin devices is very limited compared to what we have today. This means this app is very limited too. It might come in handy to control a loc not added to your Central Station, if you happen to know its address, but other than that, it’s mostly just fun.

What’s next?

Get the app from the App Store or read more about it on the RailControl Unit web page. If you have any feedback about RailControl Unit, feel free to let me know.

My best wishes for 2026, and most importantly: have fun!