Square and Jack Dorsey never ceased to amaze me, and today after reading about their big announcement on Square Register, I went back to dig a bit about their technology, and ran into a good talk by Bob Lee and Eric Burke, found here.
My God, this is serious technology that made use of all the math and signal processing that we learned in school, and never thought we would use it again. Listening to the talk, I felt that I understood a bit more about the art of engineering, which is to make things work given what you got. There are not perfect solutions to every problem, but there are good approximations. And engineering is about finding these approximations that get the job done.
All the theories are theories, sometimes they are useful, and sometimes they are not. You pick something that is useful, but engineering is about finding that theory and applying it to your problem.
The card reader is a mic, and a swipe registers a signal. Using signal processing techniques, Square can induce card numbers, validates it, then passes it for the credit card company to do its own validation. There’s a lot more to it that I don’t understand, but for now, all I can say is, wow!