Though we rarely stop to think about it, there’s a small fortune sitting in plain sight in almost every convenience store and gas station. Any time you stop at an ATM to take out some cash, you’re standing in front of a tiny vault that can hold up to $200,000 in cash. But while it might sound insane to leave that much money out on the street, ATMs are actually amazingly high-tech—and well protected—devices.

In the video “How ATMs Work,” the Science Channel explains how ATMs keep money safe, and how they always manage to give the right number of bills to customers. In just three minutes, the video explains how sensors, rollers, and conveyors inside the machine ensure its accuracy, and how an incredibly heavy safe inside the device protects all that cash from theft. “Four hundred parts work together,” the narrator explains. “It’s like Fort Knox in a box.”

[h/t Gizmodo]

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