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Magnetic Card Reader Instructions

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Magnetic Stripe Reader Instructions This lab will demonstrate how magnetic stripe readers operate. Although they are sophisticated devices, they operate on basic principles which we will observe in class. I. Assemble the reader I. Connect the reader as shown in the above photo o Banana A: +15V o Banana B: Gnd o Banana C: -15V o BNC1+: T2 to AIN0+ o BNC1-: Gnd o BNC2+: T1 to AIn1+ o II. BNC2-: Gnd Set up LabView II. Download the vi from the wiki and unzip it and open the .llb file o Double Click on Read2Tracks o Click the Run arrow and swipe a card. 0 1 III. Decode the signal o The account number is encoded binarily using F2F encoding. A “one” as shown above has 2 peaks in the bit time. A “zero”, also shown above, only has 1.  The magnetic stripe is encoded with leading and trailing 0’s so that you can measure the initial bit time. o IV. V. VI. After this, the number will be encoded as sets of 5 binary characters (See Character Set)  On a forward swipe, the data is organized least significant bit first (B1) to most significant bit (B4) followed by the parity bit.  The Start Sentinel is the first character encoded on the card and has the format: 01011 when 1 is the LSB  The last bit is the parity bit. This is an error detecting device. On the magnetic stripe reader, the parity bit will be 1 if there are an even number of high inputs, and 0 if there are an odd number. You can read more about parity bits here.  If the parity bit doesn’t agree with the input you wrote done, go back and check that your 0’s and 1’s are right. o Try to decode the cards provided. What is the code? o If you finish that, try decoding you WashU ID or room key. Do you notice anything familiar about the numbers? Explore Magneprint o Zoom in very closely on a magnetic “zero”. What do you see? o Notice the slight variations in the voltage – this is not a pure tone at all. o These variations are caused by the random arrangement of magnetic fields on the card stripe. These are known as Magneprint, and they are unique to each card. o Using Magneprint could help reduce identity theft (skimming) dramatically. Compare the Magneprint from 2 swipes of the same card. Look at the same place on the card in both cases. Compare the Magneprints from 2 different cards. Can you tell them apart?