twork is its physical layout or shape. 2. Baluns in leads. There are four basic topologies: bus, ring, star and tree. 3. Balun in adaptor at socket end. The star has the advantage that one end of each cable comes back to a common point. This enables changes to be made at one place. Considering the socket outlet end the balun/adaptor can be located By linking the legs of the star together, bus, tree and ringlike at the terminal or socket outlet end of the terminal lead. structures can be created. 33/6 Structured cabling Structured cabling systems have a star topology while the network shown. The data rates required are achieved by UTP cable but there that is to be implemented can be bus, ring, star or tree. The solution is minimal spare bandwidth for combining on copper. is to make the network into a local star. That is, the last 100 metres Fibre optic multiplexing provides a solution for the data concen- from the desk is a star. This is achieved with patch panels plus the trations in the riser (vertical) part of the structured cabling system. devices given in Table 33.4 depending on the basic network being There are two approaches to the fibre multiplexed backbone. One used: is to have independent fibres for each service and the second is to combine them into a common fibre system such as FDDI (Fibre Table 33.4 Network topology, services and conversion Distributed Data Interface). The two main issues are the cost of the fibres against the cost of the equipment to combine different services onto the same network. Network Service Conversion device The simpler, cheaper and most robust solution today is to provide independent fibres for each service. Although a common system Ethernet Multiport transciever/hub unit with one network management system does have its benefits. Daisy Chain Twinax Loop wire concentrator Fibre backbones are generally based on a fibre patching system Token Multiple access unit with fibre to copper interface devices in wiring closets and 50/125 or 62.5/125 multimode graded index vertical fibre