The DESCount card contains credits that are used to upgrade existing Mifare Convexs/Invexs readers to make them capable of reading Mifare DESFire cards. In case a Convexs or Invexs reader is ordered for reading Mifare cards the reading functionality for DESFire cards is disabled. Presenting the DESCount card to the reader enables this functionality in the Convexs or Invexs reader. A DESCount card is ordered per license and can be used to changes up to 1.000 card readers of an installation.