Abstract: An information card system according to the present invention establishes a data communication between a terminal unit and an information card after receipt of an acknowledge signal supplied from the information card to the terminal unit, and the acknowledge signal is produced by a combination of a periodical signal retrieving circuit and an output unit incorporated in the information card upon receiving a periodical signal fed from the terminal unit, so that a misfit between the information card and the terminal unit is detectable before the data communication.

Abstract: An integrated circuit card having a one-chip micro computer, a memory, and an address bus and data bus for coupling the micro computer and the memory, includes an input/output bus and interface for communication with an external terminal device. The micro computer executes processing commands from the external device, and returns the processing results to the external device through the interface. Instead of returning the processing results to the micro computer immediately when processing is finished, the IC card includes a timer for measuring elapsed time starting with the receipt of a processing command. The processing results are returned to the external device only when a predetermined elapsed time has been measured by the timer.