A process and equipment for safeguarding the operation of gambling machines with electronic cards in a manner that protects against counterfeiting and fraud. The microchip cards are numbered and a central computer stores at least the amount paid in for playing under the particular card number upon issuing the card. A card is inserted in a gambling machine, which has a read/write unit that compares the amount available for playing with the credit stored under the respective card number in the central computer before releasing the gambling machine for playing. Only if the two amounts match is the machine released for playing and the prevailing credit balance for the card is transmitted continuously during play to the central computer.