Magnetic stripe encoding explained  

Track 1: Developed by the International Air Transportation Association (IATA), track 1 contains alphanumeric format of 79 alphanumeric characters, at 7 bits per character with information for applications such as automation of airline ticketing or other transactions where a reservation database is accessed.

Track 2: Developed by the American Bankers Association (ABA), track 2 contains numeric information encoding of 107 numeric characters at 5 bits per character for the automation of financial transactions. This track of information is also used by most systems that require an identification number and a minimum of other control information.

Track 3: Developed by the Thrift Industry, track 3 contains information, some of which is intended to be updated (re-recorded) with each transaction (e.g., cash dispensers that operate “off-line”).magnetic stripe is encoded with bit patterns, which correspond to alphanumeric (Track 1) or numeric (Tracks 2 & 3) ASCII characters. The number of bits on a given track is limited to a certain number of bits per inch, or BPI. There are also a series of all zero bits encoded at the beginning and end of a magnetic stripe; these “clocking bits”establish timing for the reader, or the time the reader will detect flux reversals as it moves down the magnetic stripe.