A marine gangway to enable handicapped users to move between floating and fixed landings may include a gangway ramp extending between the floating and fixed landings, and at least one rail carried by the gangway ramp. Upon receiving a write request to a memory cell array including a variable resistive element where information is stored based on a resistance state of a variable resistor, an inputoutput buffer outputs write data to a write control unit and an ECC control unit. An amount of adjustment of a polarization controller is determined based on the signal degradation, the amount of adjustment being selected to reduce the polarization mode dispersion. With this constitution, it becomes possible to generate a stable horizontal drive pulse which causes no jitter on the screen when a PIN balance correction, a KEY balance correction and a horizontal position adjustment of a CRT are performed by digital processing. The safety is triggered by this output from the optical fiber sensor. First and second protrusions extend outwardly from the shutter member and are slidably and pivotally received in the first and second grooves, respectively, in the base member.