The invention relates to the design of card readers for cards equipped with memory. Such cards, and also the data stored in the memory of such cards, are generally utilized to produce and/or maintain operating states of technical devices. It is also known that the user personally can store data in certain areas of the memory. However, as the memory design and usage has been standardized for the most part and the memory capacity reserved for use by the user is relatively small, the memory capacity reserved for the user can only be increased by providing the device with additional cards equipped with memory. However, as all cards used in a device to supply the full functionality mast operate together in a prescribed manner, it is the task of the invention to specify a card reader that organizes this operation. To accomplish this, it is specified that a monitoring device 17 or a closing device 24 is present that prevents the insertion of a second card 11.1 when there is a first card 11.2 inserted in the first slot 12.2, or that ensures, when there are two cards 11 in the slots 12, that the first card 11.2 is removed from its corresponding slot 12 before second card 11.1 is removed.