To easily change a standby screen of a corridor lamp by reducing the number of steps of operation in changing the standby screen of the corridor lamp by a nurse call master unit.

A bed screen showing images set as display images for corridor lamps of respective sickrooms as set thumbnail images 31_-1-31_-6 is displayed in a display of a nurse call master unit. When operation of selecting a set thumbnail image for an optionally selected sickroom is performed on the bed screen, the selected set thumbnail image is directly transferred from the bed screen to a display data selection screen showing a list of a plurality of thumbnail images for selection 32_-1- 32_-n, so that it is not necessary to perform a number of steps of operation through hierarchical menus before reaching the display data selection screen, and the standby screen of the corridor lamp can be easily changed with fewer steps of operation.