What Is a UTP Patch Cable?

A patch cable is a length of cable sold with connectors already installed on either end. UTP is Unshielded Twisted Pair cable, which is the most widely used cable type for Ethernet networks. Ethernet is the most widely implemented set of standards for the physical properties of networks.

The Ethernet standards are produced by the Institute of Electrical and Electronics Engineers. All Ethernet standards come in versions indicated by the 802.3 code followed by one or two letters to indicate a series. Products conforming to Ethernet standards will have the version of those standards printed somewhere on the packaging, or in their user guide. Different standards allow different categories of performance.

Unshielded Twisted Pair is so closely identified with the Ethernet standards that it is often referred to as Ethernet cable. A UTP patch cable will be advertised in computer stores as "Ethernet cable." This is not strictly true. Unshielded Twisted Pair is one of the cable types recommended for Ethernet networks. Other types currently recommended are single-mode and multi-mode fiber optic cable and twin-axial cable. However, computer stores never label these cable types as "Ethernet cable," only UTP. The fact that the bagged Ethernet off-the-shelf cable found in computer stores already has its connectors installed makes it, strictly speaking, patch cable, and not just UTP cable.

Unshielded Twisted Pair is so common in networks because it is cheaper than the other forms of cable recommended by Ethernet standards. It is cheaper because it does not require a metal shield to be embedded beneath the plastic jacket of the cable. The shield in other cables protects the wires within from environmental magnetic interference. In UTP pairs of cables are twisted together. The two wires in the pair represent the positive and negative wires of a complete circuit. When a current travels along a wire, it creates magnetic field around that wire. Environmental magnetic interference merges with that magnetic field. When the positive and negative wires are twisted around each other, their magnetic fields cancel each other out, taking the environmental magnetic interference with them.

Patch cable is a prepackaged stretch of network cable that can connect a computer to a router, a switch or hub. It cannot connect a computer to a computer, or a computer to a printer. This is because the computer listens to two wires in the cable for incoming data and it sends data out on two other wires. Two computers connected by a patch cable would listen on the same circuit and ignore incoming signals on the transmit circuit. Computer to computer connections require crossover cable, which switches the wiring of the transmit and receive paths in the connector at one end of the cable.