Abstract: A plug-in data carrier includes a processor, a program memory connected to the processor, and a dedicated memory connected to the processor. The dedicated memory is divided into a plurality of regions including a region for controlling and managing the operation of a transaction device, which is a device independent of the plug-in data carrier. The transaction device includes a first contact section which establishes electrical contact with the plug-in data carrier, a second contact section which establishes electrical contact with another data carrier, a first memory section inputting and outputting data to the plug-in data carrier via the first contact section, a second memory section inputting and outputting data to the another data carrier via the second contact section, and an interfacing circuit.