The correlation between a device on the sending side and a device on the receiving side can be controlled with a high degree of freedom when sending and receiving data between multiple devices. A POS system 1 includes a host device 11 with a storage unit 25 having a data storage box 26 that stores data, and a transmission unit that sends data the data storage box 26 stores when data is stored in the data storage box 26; and a display tablet 102 that receives and displays data sent by the host device 11. The display panel 102c of the display tablet 102 is linked to the data storage box 26 of the storage unit 25 of the host device 11.