igurations. You can buy a cable containing two pair or four, eight, twelve, twenty-five 248 The Telecom Handbook CHAPTER 12 or fifty pair (CAT 5E only up to 25 pair). The most frequently used cable, which is a standard, is a 4-pair cable (total of 8 wires). By definition, Categories 5E and 6 are both 4-pair cables. Each pair of wires within a cable is color coded. For ex- ample, one wire is blue with white stripes. It is twisted around a second wire which is white with blue stripes = white/blue- blue/white. There is also white/orange-orange/white, white/ green-green/white, white/brown-brown/white, etc. In many installations, more than one 4-pair cable is run, perhaps two 4-pair cables or, most commonly, four 4-pair cables. Some forethought is required in terms of how the cable is to be used, although the planned use may be different from the ultimate use. Jacks In addition to deciding how much and what type of cable will be run, it is important to consider how the cable will be termi- nated at each end. At the desk, the end of the cable will terminate in a jack into which a connector will be plugged to connect the telephone or other communications device. Sometimes the con- nector is referred to as the jack, but the jack is actually the outlet. The means for terminating the cable, and the size and con- figuration of the jack are dependent upon what is to be plugged into the jack, which is not always known when the cable is run. For example, it is possible to terminate all eight wires of a 4-pair UTP in an 8-pin modular jack. The Category 5E and 6 standards require that you do so. It is also possible to terminate only six of the eight wires (or fewer), leaving one or more spare pairs in the wall behind the jack. This is called a split cable. The spare pairs can also be terminated on a second jack. The connec- tors plug into the jack, ideally having the same amount of wires as are terminated on the jack. It is possible to plug a 6-pin con- nector into an 8-pin jack, but it is not recommended in terms of ensuring th