Compared to the word processors on our phones and computers, typewriters seem fairly low-tech. They don’t need microchips to translate your keystrokes into words on a page—just old-fashioned, analog machinery. But calling these devices unsophisticated would be inaccurate. As the video below demonstrates, there’s a lot going on beneath the hood of a typewriter.

The Hursley Museum in the UK shared this video of IBM’s Selectric typewriter in action to its YouTube channel. According to Nerdist, it shows the innovative “golf ball” element that made the device unique. Instead of using individual typing arms connected to each key, this 1961 invention uses a spinning ball. The ball is covered in typeface characters.

When the user punches a key, that activates a system of linkages, which results in the tugging of two cables. One cable spins the ball sideways and the other tilts it vertically. Together, they dictate which character hits the typewriter ribbon (the strip that transfers ink to the paper). Each key triggers its own unique tugs associated with the corresponding character on the element.

Even after reading about how it works, seeing the gear move is impressive. Initially, the video shows the machine typing at regular speed. When the video slows down to 960 frames per second, it’s easier to track the golf ball element’s movements.

The Selectric typewriter is one example of how the typewriter evolved after its invention in 1867. You can learn more about the history of the typewriter here.

[h/t Nerdist]