A terminal 50a functions as a signal terminal when a first PC 30 and a first port replicator 50 are connected to each other. A terminal 60a functions as a power terminal when a second PC 40 and a second port replicator 60 are connected to each other. Thus, even if the PC or the port replicator becomes multifunctional, it is possible to suppress a significant increase in the number of pins of the connectors 11 and 23. Further, it is possible to keep up with functionally improved PCs and port replicators while maintaining compatibility with the past products.