Magnetic-stripe, read and decrement


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; and
  • Magnetic-stripe readers, read only, which provides information about magnetic-stripe readers and how they are used in read-only applications.

This section considers only the relevant differences when the reader should read and also decrement. For read and decrement, there are some differences about the reader technology and its functionality:

  • The reading head must have read / write capability.
  • In most cases, a printer unit will be required, to print information about the current trip / day of validation, and to show the trips / value remaining.
  • The software must be able to process the transaction in real-time. This includes determining what deduction should be made, whether there is sufficient value or units for the proposed travel, calculate the new balance, and prepare the new data to be written to the card. 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 the passenger transport domain, the following applications require magnetic-stripe readers with decrementing functionality:

  • Single tickets, which have been pre-issued. Their value is adjusted so that they cannot be used again for a new trip (allowing that timed transfers may still be permitted).
  • Multi-journey tickets, to determine whether a new trip has commenced (allowing for time transfers) and, if so, to reduce the number of remaining journeys by one.
  • Multi-day tickets, to determine whether there is a current day active and, if not, to activate a new day and reduce the number of remaining days by one.
  • Stored value tickets, to deduct the tariff to be paid from the available balance and to calculate the new balance. If the available balance is less than the required tariff, to apply the rules – which are either to decline the transaction, or to allow the trip if there was any non-zero balance but then to set the balance to zero so further trips cannot be made.

In all cases, the validation details and number of remaining units (journeys, days, stored value) are printed on the ticket as a receipt and information for the customer.

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

  • Supports a range of multi-journey, multi-day and stored value fare products.
  • Prints information to the ticket for customer information.
  • Allows information to be written to the magnetic stripe.

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

  • Cannot support secure electronic purse.
  • Consumables such as printer cartridges can be expensive, and must be maintained and replaced.
  • The machines must have a card transport mechanism, a printer and a read/write head. This introduces moving parts and the complexity of the electronics and interfaces among the components. This requires technical capacity of the operator, and has more risk of failures. 
You are here Technologies Ticket reader and decrementer Magnetic-stripe, read and decrement