They are operated either pneumatically or hydraulically. The press (or actuator) supplies the clamping force pneumatically or hydraulically. Stage separation is accomplished with explosive bolts and a pneumatically actuated pusher system. These systems are however limited to use on pneumatically actuated valves. They first appeared in the 1900s, when they were actuated either mechanically or pneumatically. Instead, a French two-position pneumatically actuated Ratier type was substituted. The impulse to open the valve is transferred by a pneumatically mechanical controlled controller unit. A longitudinal driver-controlled pneumatically operated differential lock is fitted. Both axles are fitted with driver-controlled pneumatically operated cross-axle differential locks. Both are fitted with driver-controlled pneumatically operated cross-axle differential locks. They were then replaced by pneumatically operated switching elements. Nearly all rivet guns are pneumatically powered. It manufactured pneumatically controlled music automatons, above all orchestrions. The Touring version features a pneumatically suspended rear axle. Big Shot is a pneumatically powered tower ride.