Every home and office has switches, for the control of lighting or switched receptacles, and duplex or single receptacles for 120V power to appliances and equipment. These devices have varying designs, from the conventional to decorator styling for aesthetics. Even though these devices are commodities, they nevertheless are necessary components of 120V branch circuit wiring in electrical distribution systems in residential, commercial, institutional, and industrial.


Switches, or "snap switches" as they are sometimes called, come in single-pole,'way (SPDT), and 4-way configurations for single, double, or multiple control locations respectively. Various colors are available as well as pilot handles; the handle lights either when the load is switched ON, or when the switch is in the OFF position. This functions enables you to locate the device in the dark.

Switches are either AC or AC/DC, with their application depending on the type of load involved. T-rated switches are used for circuits containing tungsten-filament lamps.

Dimmer switches are also an important component of branch circuitry. They come in varying wattage ratings and styles. Some have rotary handles while others have slide handles, or even touch pads. These switches tend to be more decorator styled. Most fit into standard single-gang wall boxes. Some dimmer switches require fins on their fronts to allow for heat dissipation; the higher the connected wattage, the more fins required.

Dimmers are available for both incandescent light sources and fluorescent light sources. Receptacles and plugs Receptacles and plugs in straight blade designs are usually rated 15A or 20A, 125V, although specialized configurations are available for higher currents and voltages. Locking types are also available where pull out is to be prevented.

GFCI (ground fault circuit interrupter) receptacles are devices that interrupt the electrical circuit to the load when a fault current to ground exceeds a predetermined value that is less than that required to operate the overcurrent Protective device of the supply circuit. As such, they are primarily used for personnel safety. They are required in residential and commercial occupancy bathrooms, residential garages, and outdoor installations. This type of receptacle usually has an integral test button on its face, and may also have a reset button to re-energize the receptacle after testing. Some models feature a feed-through capability where the receptacles attached downstream will also be GFCI protected. These downstream receptacles must have labels affixed to them denoting their protection characteristics for the end-user.

GFCIs come in ratings of 15A, 20A, and 30A. Isolated ground receptacles are devices used to reduce the transmission of electrical noise (electromagnetic interference) and have orange faceplates or an orange triangle on the device face. Sec. 410-56(c) of the NEC defines their construction and color designation.

Surge strips

Most offices and locations where personal computers (PCs) are used have surge strips located very near. They consist of multiple plug-in devices in one module, with the module itself being cord-and-plug connected to a 120V source. Their function to provide protection against surges, spikes, and sometimes EMI/RFI noise, so that sensitive electronic equipment will function properly. They are considered as point-of-use protection. These devices may have 125V electrical receptacles in 2-, 4-, or 6-outlet combinations, or have data and phone outlets capable of accepting RJ-11 or RJ-45 connectors. Some units feature all three. Most have integral fuses and resettable circuit breakers ahead of the protected devices.

Most surge strips will have a UL clamping level,for example 400V peak,that states the performance level of the device.

Newer devices are used primarily on FAXs.