Abstract: One of a pack of flexible cards is removed from a container and placed in a recess in a telephone set. The cards serve as small, portable directories for a plurality of subscriber numbers. Four repertory buttons take the form of a touch-sensitive keypad and are disposed in the bottom of the recess under the respective inscription areas of the card. An electronic telephone number memory is built into the telephone set together with a microprocessor and a line and dialing unit. The cards further include either a combination of notches as a four-bit card identification or an optical three-bit identification. The notches are detected by electromechanical feelers in the recess and, together with the repertory buttons, determine the storage addresses of the telephone numbers. In the case of optical identification, each card comprises an inscription carrier and, adhering thereto, a transparent cover film which can be removed and replaced a number of times.