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Let’s take a look at why the wires in this cable type are twisted. When electromagnetic signals are conducted on copper wires that are in close proximity (such as inside a cable), some electromagnetic interference occurs. In this scenario, this interference is called crosstalk. Twisting two wires together as a pair minimizes such interference and also provides some protection against interference from outside sources. This cable type is the most common today. It is popular for several reasons:


■    It’s cheaper than other types of cabling.


■    It’s easy to work with.


■    It permits transmission rates considered impossible 10 years ago. UTP cable is rated in the following categories:


Category 1 Two twisted-pair (four wires). Voice grade (not rated for data communications). The oldest UTP. Frequently referred to as POTS, or plain old telephone service. Before 1983, this was the standard cable used throughout the North American telephone system. POTS cable still exists in parts of the Public Switched Telephone Network (PSTN).


Category 2 Four twisted-pair (eight wires). Suitable for up to 4Mbps.


Category 3 Four twisted-pair (eight wires), with three twists per foot. Acceptable for 10Mbps. A popular cable choice since the mid-80s.


Category 4 Four twisted-pair (eight wires) and rated for 16Mbps.


Category 5 Four twisted-pair (eight wires) and rated for 100Mbps.


Category 6 Four twisted-pair (eight wires) and rated for 1000Mbps. Became a standard in December 1998.


Frequently, you will hear Category shortened to Cat. Today, any cable that you install should be a minimum of Cat 5. This is a minimum because some cable is now certified to carry a bandwidth signal of 350MHz or beyond.

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