Automotive service technicians and mechanics, often called service technicians or service techs, inspect, maintain, and repair cars and light trucks. Service technicians work on traditional mechanical components, such as engines, transmissions, and drive belts. However, they also must be familiar with a growing number of electronic systems. Braking, transmission, and steering systems, for example, are controlled primarily by computers and electronic components. Other integrated electronic systems, such as accident-avoidance sensors, are becoming common as well. In addition, a growing number of technicians are required to work on vehicles that run on alternative fuels, such as ethanol and electricity. Service technicians use many different tools, including computerized diagnostic tools and power tools such as pneumatic wrenches, lathes, welding torches, and jacks and hoists. Service technicians also use many common hand tools, such as sockets and ratchets, wrenches, and pliers. In fact, experienced workers often have thousands of dollars invested in their personal tool collection. For example, some invest in their own set of pneumatic tools—tools, such as impact wrenches—powered by compressed air. Service technicians sometimes specialize in a particular type of repair that may be subject to specific regulations or procedures. For instance, those focused on repairing air-conditioning system must follow federal and state regulations governing the handling, recycling, and disposal of refrigerants.