ble location, the office floor area is laid out in a 6 metre 120mm to 150mm or 200mm. grid. Locating a floor box in the middle of each 6 metre square, containing two voice and two data outlets, will provide adequate communications cover. Wiring all of these outlets back to the patch System components panel(s) on that floor will provide "flood wiring". Modern buildings are designed for a life of about 50 years, while The major system components are: the computers and PABX equipment is bought to last between 3 and 10 years. 1. Distribution frame/patch panel in IT room. It is reasonable to plan for a major refurbishment every 12 to 15 2. Riser cable - fibre or multicore copper. years. It is important that the cabling system is geared to the building 3. Active hub technology equipment - multiplexer, MAU, etc. elements and not to the installed communications system. 4. Patch panel per wiring closet. It is also important that minor changes can be performed quickly 5. UTP horizontal cabling. and efficiently. To get this flexibility the initial installation cost will 6. Socket outlets. be higher but the system will last longer and changes will be less expensive. There is a choice of seven basic cable types shown in Table 33.2 with the data rates currently being used on them. 33.2.1 Wiring closet location Unshielded twisted pair (UTP) is a number of individually twisted pairs in a common outer sheath. The laylength of the twists are The most basic limitation on the positioning of telecommunications arranged to be different between each pair to reduce the crosstalk closets is the need to keep the lengths of cables within the limits set between pairs. The term laylength is a measure of the length along by the structured cabling scheme that will ultimately be used. Most the wire taken by one complete twist. can provide 100 metres and this is the limit given in the emerging Unshielded twisted pair with an overall screen is of a similar Electronic Industries Association (EIA) standard. This distance is construction but with an