Types
Power and Control Tray Cable (Type TC)
TC cable is defined by the NEC as “a factory assembly of two or more insulated conductors, with or without associated bare or covered grounding conductors under a nonmetallic sheath, for installation in cable trays, in raceways, or where supported by a messenger wire.”
Power Limited Tray Cable (Type PLTC)
PLTC cables are specially designed for power-limited circuits, such as burglar alarms, intercoms and cash registers. Unlike TC cable, which is rated for 600 volts, PLTC cable is rated for 300 volts only.
Instrument Tray Cable (Type ITC)
ITC cables are a relatively new designation. It is fire resistant and rated to 300 volts, but can only be used for 150 volt applications.
Optical Fiber Cables
Also referred to as “fiber-optic” cables. These cables are completely different from the typical electrical cables, in that the fibers do not conduct electricity. Signals are transmitted through the fibers using light. An optical fiber cable consists of a bundle of optical fibers. They also save space, because more signal is carried through the smaller fibers compared to regular cables, and also do not react to electromagnetic interference (EMI).
Fire Alarm Circuit Conductors
Fire alarm cable must adhere to strict regulations, due to their sensitive use. They must be flame resistant. Depending on the installation situation, they can be power limited, or non-power limited.
Communication Cables
Communication cables are different from power cables in that they do not transmit high amounts of signal and voltage. They’re used to transmit data at high frequencies.
Mineral Insulated (MI) Cable
MI cables are special-application cables, and are made of a center copper conductor, magnesium oxide insulation and an outer sheath. Because magnesium oxide is not an organic material, this type of cable is the most fire resistant cable available. As such, it is used for the most critical fire resistant applications: fire alarms, nuclear reactors, emergency power systems, etc.
Metal Clad (MC) Cable
MC cables have a metal tube shield over the center conductor, sometimes followed by an outer jacket. The outer jacket helps protect the metal shield from corrosion. For certain applications, a corrugated shield or nonmetal jacket must be used to comply with the standard.