There are five connections you will need to make (four if you don't mind giving up more fine tuned control for fewer I/O ports being used). In this 'ible, I'm going to show reading from the primary first track to get you started. This card reader's data is valid 1.0 us before the strobe is put onto the line, so there's no worry about delaying to get yourself into the 'bit time.' For a dual head reader such as the one I'm using, there are two data tracks available to read. Reminds me of having to change the setting for her that determines how much time is valid between clicks to register a double-click. Self-clocking allows even my sweet grandma the ability to use her card without breaking her wrist. This make sense when you think about card swipes: everyone swipes at a different pace, some slower, some faster than others.

It means you don't have to worry about looking for a clocking signal and timing the signal to center directly on the clock pulse, and no bothersome oscillating into the sweet spot of the clock signal.

Magnetic card readers are 'self-clocking,' meaning that they provide a clock called a strobe, against which the connected microcontroller can sync.

Arduino magnetic card reader and writer