Fri 9 Jun 2006
With so many magnetic cards in our wallets/money clips/purses, some times we wonder what information is exactly stored there. The first step is to determine which card standard needs to be decoded. The popular formats are ISO1, ISO2 and ISO3 which are the magnetic stripes 5.5mm, 9mm and 12.5mm from the card edge respectively. Next, a card reader must be obtained. It is possible to construct your own reader by using cassette tape heads, however, card readers are readily on both Ebay and Digikey for reasonable prices ($5-$40). Most cards have either ISO1 or ISO2 data which features some padding that determines the scan direction. Having said that, readers are available that support multiple ISO formats on the same device. With These devices generally offer three control lines (per track): card present, data, and clock. The card present is good for interrupt control and the other two are for standard data retrieval. With this information and a reader, the information can be readily extracted and processed, however, there also exist expensive magnetic particles suspended in liquid solvent that will allow visual inspection of the magnetic data without the need for a reader.
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