Magnetic stripe, read and write


This section should be read in conjunction with:

  • Magnetic stripe tickets, which provides information about magnetic stripe tickets and describes the applications for which they are used;
  • Magnetic stripe readers, read only, which provides information about magnetic stripe readers and how they are used in read-only applications; and
  • Magnetic stripe readers, read and decrement, which provides information about magnetic stripe readers that have decrementing, printing and read/write functionality and how they are used for decrementing applications.

This section considers only the relevant differences when the reader should read and write, compared to read-only. For read and write, there are some differences about the reader technology and its functionality:

  • The reading head must have read / write capability.
  • It depends on the intended use as to whether a printer unit will be required. If the reader should activate a time period (e.g. day ticket, week / month pass) then a printer will be required to show the start / expiry date / time in the ticket.
  • Depending on the intended use, the software may require to process the transaction in real-time. As described in the read-only section, this can either be self-contained in the reader, or the reader may need to work in real-time with a connected device (e.g. ETM, station server)
  • Manual swipe / insertion is not practical as the reader must read the original data, write the new data, and then read again to verify that the card has been completely and correctly updated.

In practice, almost all magnetic-stripe readers used for fare collection in public transport have read / write capability (as a minimum). As most transit agencies offer fare products that require read and decrement capability – or anticipate that they may have such products in the future – there is a requirement to have both read / write and read / decrement functionality. Consequently, most magnetic-stripe readers used for fare collection have both functionalities.

In the passenger transport domain, the following applications require magnetic-stripe readers with read and write functionality:

  • Time period tickets, which need to be activated. The reader sets the activation time or the expiry time of the card (or both) and prints the information on the card. Subsequent validations recognize the ticket as an active travel pass and will accept it up to the expiry date.
  • Single tickets, which have been pre-issued. The validation data is written to the stripe and the printed on the ticket. No decrementing function is required, but the ticket will not be accepted for a new trip (allowing that timed transfers may still be permitted).
  • Boarding information. In most systems, information about the current boarding is written to the strip for transfer, revenue protection and/or planning data reasons. This is done even when no adjustment needs to be made to the values on the ticket.

Benefits of read and write magnetic-stripe readers (relative to read-only readers) are:

  • Supports a range of travel passes.
  • Writes transaction data to the ticket, which can support time transfers and revenue protection.

Cautions with regard to read and write magnetic stripe readers (relative to read-only readers):

  • If the reader does not have a printer unit, may be limited in the range of fare products that can be supported.
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