Electrical contracting services install and maintain electrical distribution equipment; interior, exterior and municipal lighting; security systems and closed circuit television systems (CCTV); and information technology or IT systems. They differ in terms of capabilities and are staffed by master electricians, apprentices, journeymen, and trained technicians. Electrical contractors who work for builders connect wires to circuit breakers, transformers, outlets and other electrical components. They use hand tools such as crimpers, strippers, screwdrivers, knives, wrenches, hacksaws, pliers and polishers. Electrical contracting services also use testing equipment such ammeters, ohmmeters, voltmeters, and oscilloscopes to test the wiring and cabling in buildings, factories, hospitals, and other facilities.