ly recognised standards to carry a wide range of voice and data services. This is the key to a structured cabling system. 33.2 Structured cabling A structured cabling system is an ordered building voice and data wiring system which uses internationally recognised media in ver- tical riser backbones and in horizontal floor distribution. Wiring In the past, most offices were wired to suit the installed computer closets are located at the interception of the floors with the risers. system. That is, the cable was specified by the data equipment Patch panels in the Information Technology (IT) room and the manufacturer. The building then had a variety of cable types to suit wiring closets provide flexibility to route any signal from the IT the range of data systems installed. room to any workplace on any floor. The medias - usually fibre in Changing the computer system would result in changing the cable the riser and UTP in the horizontal - are used to carry a wide range and hence rewiring the building. of services with capacity for future services. Table 33.1 Services handled by structured cabling systems (NA = Not applicable) Manufacturer Service Cable Ohms Zo Data rate (Mb/s) 34 36 38 Beldon 9207 AS400 Twinax Wang OIS/VS Wangnet Twinax RG59/u Ethernet Thicknet (10base5) Beldon 9880 Ethernet Thinnet (10base2) Beldon 9907 Ethernet Cheapnet (10baseT) Twisted Pair Burroughs Beldon 9272 516588+2462048 Beldon 9463 Twinax 4.275 RG62A/U Coax Token Ring 4MHz Type 1 IBM Token Ring 16MHz Type 1 IBM APPLE Appletalk/Localtalk Twinax Beldon 9999 Several RS232/V24Synchronou Multicore 0.0192 Several RS422/V11 Asynchronous 0.0192 Several Telephone Analogue 0.004 Several ISDN TIA 2.064 Several Fibre optic Several TPDDI Several 1.544 33/4 Structured cabling When a building is first wired, the tenant and his voice and data single closet, it should ensure all services can be satisfactorily needs are generally not known. To ensure there are suitable outlets distributed. This may involve increasing the floor void depth from at every possi