A method which controls modification of passwords. The fusible link tool has a holder capable of holding a fusible link and a handle connected to the holder so that the holder may be inserted into a ceiling radiation damper by a user. Further, since a machine beam can be extended at full length in the back and forth direction in the machine room, no additional building-side receiving beam is needed. Furthermore, in some embodiments, an operating state of the portable electronic device can be resolved based in part on the connection state of the portable electronic device. Also claimed is an active type liquid crystal display device of the same type as above, comprising an electrode being formed on the same layer as that of the source line, which allows the black matrix to be set as the common potential.