Abstract: Subscribers are given access to a series of events by a smart card acting as an electronic ticket, which operates automatic turnstile. A subscriber can cancel the card in respect of a particular event by telephoning a cancellation office and verbally communicating the identifying number of the subscriber's card. This number is entered into a stop list for the event. The stop list automatically controls the automatic turnstile to prevent access to the event by use of any card on the stop list for this event. Each subscriber has a hand-held reader device, for displaying a sequence number and authentication code from the card. At the cancellation office, the card is authenticated by generating a check code from the sequence number and comparing it with the authentication code communicated by the subscriber.