VERFAHREN ZUR AUSWERTUNG VON AUF KREDITKARTEN GESPEICHERTEN EINHEITEN.

摘要

Evaluation of units remaining stored on a credit card by retailers uses a device coupled via a telephone line to a central evaluation point, the credit card having personal identification characteristics. The units remaining to be consumed are stored in one or more counters (R21,R22) on the credit card. The present count condition is called from the central evaluation point at intervals unknown to the card holder e.g. random intervals, and is compared with the last known counter states, so that the account of the card holder is debited with the difference between the new and the old states. One counter may contain the personal identification number, and that counter is coupled with the second account counter on the card.