Hydraulic cylinders form the heart of many hydraulic systems. Hydraulic or pneumatic cylinders inherently produce linear motion. Factories also used hydraulic and pneumatic power. Modern telescopic ladders are either hydraulic or pneumatic. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons. Commonly, servos are electrical, hydraulic or pneumatic. Mechanical, pneumatic, hydraulic, and other systems may also use analogue signals. These suspension modifications are in contrast to lowriders, which use hydraulic or pneumatic suspensions. Steering was rack and pinion with standard hydraulic power steering. Mechanical transmission was in many cases replaced by hydraulic machinery. It is also used as a component of hydraulic and brake fluids. Air over hydraulic and full air brakes were available. Other technologies are also possible, such as mechanical, hydraulic and optical. Accumulators are a common part of hydraulic machinery. Enhanced geothermal systems can trigger earthquakes as part of hydraulic fracturing.