Four-way Switch
A set of three switches wired to control the same fixture or group of fixtures. Back to alphabetical list

Fuse
An overcurrent protection device that contains a thin strip of metal that will melt and open the circuit in case of circuit overload. Must be replaced after a circuit overload. Back to alphabetical list

Gauge
The measure of the size of a wire. The smaller the number, the thicker the wire and the higher its current-carrying capacity. Back to alphabetical list

Goof Plate
An oversize cover plate designed to hide a rough patching job around a box. Note that drywall and plaster must be repaired to within 1/8" of any box; larger gaps may not simply be hidden behind a goof plate. Back to alphabetical list

Ground
A connector that runs between a device or circuit to safely conduct current to earth. Back to alphabetical list

Ground Fault
The leaking of current to the grounding conductor. Back to alphabetical list

Ground-fault Circuit Interrupter (GFCI)
A device designed to interrupt the flow of power when a minuscule imbalance is detected between the flow and return of current. Back to alphabetical list

Home Run
In communications and structured wiring, when conductors are run from each device back to the source. Back to alphabetical list

Hot
Current is present. A hot lead is the one carrying current along a circuit. It usually has black or red insulation. A hot circuit is one in which the breaker is closed and current is present. Back to alphabetical list

Insulation
A material that is a poor conductor of current and therefore used to shield wires, cables, and connectors. Back to alphabetical list

Junction Box
A box containing splices in cables. Has a removable cover that must be accessible (cannot be buried in ceilings and walls). Also called a J-box. Back to alphabetical list

Knob and Tube
A system of wiring in which individual, loom-covered hot and neutral conductors were run using porcelain knobs to support the wires along framing members and porcelain tubes to protect wires passing through framing members. Back to alphabetical list

Knockout (K.O.)
A partially prepunched opening in a box that is removed to allow the entry of cable. A knockout that is mistakenly opened or is open because a cable is removed must be filled with a knockout seal. Back to alphabetical list

Live
Hot. Back to alphabetical list

Lug
Used to terminate a wire. Back to alphabetical list

NEC
National Electrical Code® Back to alphabetical list

Neutral
Commonly, the return conductor in a circuit. It usually has white insulation. More properly called the grounded conductor because it returns current to ground at the service panel. Note that this is different from the green-sheathed or bare copper grounding conductor that does not carry current except in case of equipment fault. Back to alphabetical list

Ohm
The measure of electrical resistance. Back to alphabetical list

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