There is provided a wavelength division multiplexing transmission system and apparatuses used therein, in which a remote apparatus to be newly added to a station apparatus autonomously sets a wavelength to be used in the remote apparatus, thereby avoiding the need for presetting a wavelength to be used in the remote apparatus. The lens device is connected by placing a hook, which is provided on a front end face of a camera main body, to a recess of a back end face. The status holding circuit is responsive to an internal node of the power up circuit for generating the active flag signal when the internal node has reached a predetermined level. The isolation switch blade presents the blade servers to the FC fabric as a virtualized N_port. The plane of rotation of the idler sprocket is tilted and offset from the planes of rotation of the drive and driven sprockets.