Twisted Pair Cables
Definition: Twisted pair is a type of cable in which multiple insulated conductors are twisted around each other in pairs and clad in a protective and insulating outer jacket. There may be multiple pairs depending on the type and size of cabling. Shielding can be added around the bundle of twisted pairs to reduce electronic interference.
Example:
Figure: Twisted pair cable.
UTP and STP
Twisted pair cable comes in two basic types: unshielded twisted pair (UTP) and shielded twisted pair (STP). As the name implies, STP includes shielding, typically a foil wrapper, around its conductors to improve the cable’s resistance to interference and noise. It tends to be more expensive than UTP and is installed only when needed.
UTP cable comes in different grades, called categories, which support different network speeds and technologies. A cable’s category is typically printed on the cable itself, making identification easy.
Category and Network Type and Maximum Speed
3 – Telephone or Ethernet
Maximum speed: 10 Mbps
5 and 5e – Fast Ethernet
Maximum speed: 100 Mbps
Gigabit Ethernet.
Maximum speed: 1 Gbps
6 and 6a – Gigabit Ethernet
Maximum speed: 1 Gbps+
7 – Gigabit Ethernet
Maximum speed: 10 Gbps+
PVC Cable and Plenum
Polyvinyl chloride (PVC) is an inexpensive and flexible rubber-like plastic used to sur- round some twisted pair cabling. However, when PVC burns, it gives off noxious or poisonous gases.
Plenum cable jacketing does not give off noxious or poisonous gases when it burns. Fire codes require that you install this special grade cabling in the plenum, which is a building’s air handling space between the structural ceiling and any suspended ceiling, under raised floors, and in firebreak walls.
Twisted Pair Connectors
The RJ45 connector is used on twisted pair cable. RJ45 is an eight-position connector that uses all four pairs of wires. Be careful not to confuse the RJ45 connector with the similar, but smaller, RJ11 connector. The RJ11 connector is a six-position connector that uses just one pair of wires. It is used in telephone system connections and is not suitable for network connectivity. The RJ in RJ11 or RJ45 is an abbreviation for “registered jack.”
Figure: An Rj45 Connector
