Patent ID: 8286259

Claim:
A network projector connected with a host computer via a wired local area network (LAN) comprising: a power source unit which supplies power to said network projector; and a display signal control unit which, when confirming that a connection confirmation signal, which is transmitted at a fixed period from the host computer via the wired LAN, is not inputted for more than a first predetermined time, outputs a supply stop signal to said power source unit indicating that a supply of power should be stopped, wherein said display signal control unit comprises: a timer which starts measurement of time when a measurement start signal indicating start of measurement of time is inputted, outputs a measurement end signal indicating that the measurement of time ends when the measured time reaches a second predetermined time, and is reset by input of a connection detection signal; a security control unit which outputs said supply stop signal to said power source unit when said measurement end signal is inputted; and a control unit which outputs said connection detection signal to said timer when detecting said connection confirmation signal, and outputs said measurement start signal to said timer when confirming that said connection confirmation signal has not been inputted within a time period during which the first predetermined time has elapsed after a cable for the wired LAN has been removed from said network projector.