Unshielded Twisted Pair Cable (UTP)

Two copper wires, each encased in its own colour-coded insulation, are twisted together to form a twisted pair. Multiple twisted pairs are packaged in an outer sheath, or jacket, to form twisted-pair cable. By varying the length of the twists in nearby pairs, the possibility of interference between pairs in the same cable sheath can be minimised.

Unshielded twisted-pair (UTP) cable does not rely on physical shielding to block interference, but on balancing and filtering techniques through media filters and/or baluns. Noise is induced equally on two conductors and cancels out at the receiver.

There are different varieties of UTP cable available for different needs. Basic telephone cable, also known as direct-inside wire (or DIW), is still available. Improvements such as variations in the twists or in individual wire sheaths or overall cable jackets have led to the development of cables that comply with the EIA/TIA-568 standard. These are Category 3 (up to 16 MHz), Category 4 (up to 20 MHz), and Category 5 (up to 100 MHz and greater) UTP cable.

Balun is short for balanced/unbalanced. A balun is a type of transformer that allows the connection of balanced cables (UTP for example) to unbalanced cables (BNC for example).

UTP cables are usually terminated with RJ(Registered Jacks)-45 plugs. RJ-11 plugs are usually found on telephone cables with flat untwisted wires.

RJ-11 jacks can have up to six connectors but usually only four are used.

RJ-45 jacks have eight connectors and are the connector of choice for 10baseT ethernet networks using Category 5 UTP cable.