To make realizable simplification and cost reduction of the device by making good use of an existent power-saving control function.

A personal computer 1 has a DPMS system power-saving function. Once an infrared sensor 3 detects a person, a signal S1 indicating that is inputted to a mouse interruption signal generating circuit 4. A mouse interruption signal generating circuit 4 generates a mouse interruption signal S2 on receiving the signal S1. The generated mouse interruption signal S2 is inputted to the personal computer 1 through a mouse input connector 2a. The personal computer 1 recognizes that the mouse is operated. The personal computer 1 restarts supplying driving power P2 to a display monitor 6 from an external power source 9 so as to put the display monitor 6 back to its normal mode. The driving power P2 also begins to be supplied from the display monitor 6 to a touch sensor 5.