Abstract: A bicycle includes a frame and a wheel rotatably mounted in relation thereto. The wheel is drivable by two pedal devices including pedal-equipped arms. The two pedal devices are individually mounted in different bearings and connected to the wheel via two different transmissions, which separately co-operates with a mechanical clutch. The clutch includes a dog being movable to and from opposite shoulder surfaces of which a first one guarantees driving the wheel when the dog, in an active state, is pressed against the first shoulder, and the second shoulder gives rise to noise when the dog, in an inactive state, collides with the second shoulder.

Abstract: There is disclosed a viewing window assembly for observing gas-tight and pressure-tight closed chambers of installations from outside comprising a cylindrical frame made of metal, in which is arranged a transparent insert. The frame is made of a stainless steel of low coefficient of thermal expansion and the insert is made of a glass having a similar or still smaller coefficient of thermal expansion.