The build instructions show you how to build the mechanism, without any hardware or software to keep track of time. The project logs describe how you could make this clock (or a similar one) work with a mains-based pulse generator, or (like I did) with an Arduino and a GPS module.

There is one mechanical feature that's "unique" about this clock (though I'm sure I'm not the first to think of this): unlike other mechanical clocks that usually use some sort of friction coupling to adjust the time, this clock uses a differential and a second motor. While the clock is operating normally, the differential is held stationary, so the rotation on one axle is propagated to the other axle (in opposite direction but that doesn't matter). But while adjusting the time, the time adjustment motor rotates the differential while the time keeping motor stays still.

When I was about 8 years old, I got my first box of FischerTechnik. Over the next few years, I gathered a lot more. I ended up with (what I thought was) a respectable amount of FT, that I kept adding to until I was about 16 years old. It was one of my favorite toys for a long time.

When I emigrated to the USA from the Netherlands, I couldn't take my FT with me, and it wasn't important enough to mail it, so my parents kept it in their attic. But when they moved, they didn't have space for it anymore, so they finally mailed it to me, along with a bunch of other stuff they still had.

As an experiment, I let the grandkids play with my FischerTechnik when they visited, and they loved it. So I started collecting some more of it again, especially the boxes that I knew existed and wanted to have when I was little, but couldn't, because they were so expensive. Nowadays, it's pretty easy to get FT from eBay, though some European eBay sites (especially the one in Germany of course) have MUCH more than eBay USA.

My grandkids asked me what the most complicated thing was that I ever built. I told them I once built a working clock of FischerTechnik, so they asked if I could build it again. Sure!

There is usually more than one way to solve a problem in FischerTechnik. When I first made the clock shown here, I had already made three or four other clocks. But because of the unique mechanism with the differential to set the time, I decided to take pictures while I took this clock apart, so I could rebuild it with the kids some other time, obviously by reviewing the pictures in reverse order, as shown in the Build Instructions.

I wrote an Arduino library to control the old FischerTechnik 30520 Computing interface from 1987, which doesn't work with the FischerTechnik software anymore. I added two sensor switches to the mechanism so it would be possible to sense when the hands are pointing at the 12, so the program could calibrate itself and then adjust the clock by counting pulses. The Project Logs describe two ways to do this: one way is to use the mains frequency and the other is to use the time stamp from a GPS module.