Ammeter all of the current flows through the shunt, and only a small fraction flows through the meter. This allows the meter to measure large currents. Traditionally, the meter used with a shunt has a full-scale deflection (FSD) of , so shunts are typically designed to produce a voltage drop of when carrying their full rated current. To make a multi-range ammeter, a selector switch can be used to connect one of a number of shunts across the meter. It must be a make-before-break switch to avoid damaging current surges through the meter movement when switching ranges. A better arrangement is
Electrical room enclosures of electrical equipment to prevent stray voltage and danger of electric shock, even during faults in the electrical system. Lightning protection requires different measures than protection from power-frequency faults. Electrical rooms may have electromagnetic shielding to prevent interference to nearby sensitive audio or video equipment. In large facilities access control systems may control admission to the room. Layout details and construction of electrical rooms will be controlled by local building code and electrical code regulations. Requirements for an electrical room relate to fire safety and electrical hazards. An electrical room is usually required to be secured from access by