Each apparatus transmits to a control server a notification signal indicative of a pending change or a change in an output state of the apparatus. The control server has stored therein a control rule which associates an output state of one apparatus with an output state to be taken by another apparatus when the one apparatus is in the output state. The control server acquires location-related information which is set in association with a location of each apparatus. Then, the control server receives a notification signal from any one of the apparatuses, and in response to the notification signal, determines an output state to be taken by an operation target apparatus which is other than an apparatus having transmitted the notification signal, based on the control rule and the location-related information. Further, the control server operates the operation target apparatus so as to transition into an output state determined by a determination section.