TIA/EIA recognizes three possible cabling types for horizontal wiring: UTP, STP, or fiber optic cable. UTP (unshielded twisted pair) cable is a type of copper-based cable that consists of one or more insulated twisted-wire pairs encased in a plastic sheath. STP (shielded twisted pair) cable is a type of copper-based cable containing twisted-wire pairs that are not only individually insulated, but also surrounded by a shielding made of a metallic substance such as foil. Fiber-optic cable is a form of cable that contains one or several glass or plastic fibers in its core and comes in two types: single-mode fiber (SMF) or multimode fiber (MMF). Copper-based cable transmits data via electric signals, and fiber-optic cable transmits data via pulsing light sent from a laser or light-emitting diode (LED).