Patent ID: 8374482

Claim:
A memory card attached to an external apparatus for transmitting and receiving data via the external apparatus and an optical communication, the memory card comprising: a power-supply potential unit receiving electric power supply at a predetermined voltage from the external apparatus; a ground potential unit connected to a ground potential unit of the external apparatus; a light-receiving unit receiving an optical signal transmitted from the external apparatus or another memory card; and a light-emitting unit transmitting the optical signal to the external apparatus or another memory card, wherein the light-receiving unit and the light-emitting unit are arranged such that the optical signal received by the light-receiving unit and the optical signal transmitted from the light-emitting unit are transmitted in a straight line, the power-supply potential unit is provided on any one of a plurality of side surfaces of the memory card that is disposed between a top surface and a bottom surface of the memory card and is arranged to face a power-supply potential side surface of the external apparatus into which the memory card is inserted, and the area of the power-supply potential unit is one half or less of the side surface on which the power-supply potential unit is formed such that the power-supply potential unit is completely enclosed by the external apparatus upon the memory card being sufficiently inserted into the external apparatus that electrical contact between the power-supply potential unit and the power-supply potential side surface of the external apparatus is initiated, thereby protecting a user inserting the memory card into the external apparatus from contact with the power-supply potential unit while the power-supply potential unit is at the power-supply potential.