The controller 100 causes the display device 473 to also display the work suggestion (see FIG. 9B) indicating the correct counterpart for the connector JF decided to be wrongly connected, in addition to displaying the message that the connector JF, having the light receiver R about which the decider 104 has decided that the color of received light discords with the allocated color, is wrongly connected. Therefore, the user can be made aware of how to correct the wrong connection of the connector JF, which leads to improved efficiency in the reconnection work for the connector JF.
FIG. 10A illustrates another example of the screen displaying the decision result indicating normal connection. FIG. 10B illustrates another example of the screen displaying the decision result indicating wrong connection. When the decider 104 decides that the color of received light accords with the allocated color, with respect to some of the plurality of light receivers R1 to RA, the controller 100 may cause the display device 473 to display, for example, normal connection messages NM1 to NM4, indicating that the connector JF having such light receiver R is normally connected, as shown in FIG. 10A and FIG. 10B. In this case, the user can also be made aware that the connector JF is normally connected.
