A look-ahead detection system that actively controls the suspension of at least some of the seats in a watercraft to drastically reduce the shock andor vibrations experienced by passengers within the seats caused by waves, other water conditions andor the bending of the craft as it travels through the water. The system comprises an optical monitor that receives a portion of an outbound signal from an optical network and generates a switch control signal based on the intensity of the outbound signal. In at least a part of a portion of the electrode bar embedded in the sealing portion, the entire outer peripheral surface thereof is covered tightly with a metal-foil sleeve 7a. The exhaust outlet coupling member is in close contact with an upper wall of the toner container around an exhaust outlet, and includes a skirt made of elastic silicone rubber that covers a joint part of the exhaust tube and the air outlet.