Abstract: Card reader for game machine with a memory (42) which contains a minimum credit value and receives the credit value available from a card. At each stage of the game, the available credit value varies. The available credit value is compared, on each transaction, with the minimum value. When the available credit value is less than the minimum value, a circuit (47) triggers seizure of the card. A reader of this type can operate by performing all transactions in a memory within the reader, only reading the card memory when the card is inserted into the reader and updating it when the card is ejected.