PURPOSE: To improve the portable performance without using an accessory while keeping interchangeability with a conventional data communication interface.

CONSTITUTION: The equipment is provided with a case 12 plugged into a receptacle provided in an external terminal equipment 2 with a physical shape in compliance with standards and having an interface section 14 in compliance with predetermined standards, an information section 221 provided in the case 12 and storing card attribute information required for communication of data of the terminal equipment 2, a voice input section 122 receiving a voice signal at taking, a voice output section 112 outputting the voice signal, and a modulation demodulation section 222 modulating/demodulating data of the terminal equipment 2 based on the information stored in the storage section 221 when the case 12 is inserted into a receptacle provided in the terminal equipment 2 and modulating/demodulating the voice signal in the case of talking.