Telecom/data networks

See Figure 13-2 for an example of how EMI suppression techniques are applied to dc-dc converters. We have shown an industry standard isolated brick (along with its external EMI filtering). The input to this particular module is a coarsely regulated 18 V-dc or -60 V-dc bus, forming part of a distributed power architecture for a data/telecom network. Its output is isolated and regulated (e.g. 3.3 V/50 A or 12 V/10 A etc). The -48 V-dc input is usually derived from an off-line telecom power supply (called a rectifier ). 

Data can be collected automatically and stored either for download to a portable computer brought to site or by telecoms connection where the engineer can connect remotely to the computer and download data. The data in Figure 5.3 was collected on a central computer from networked sensors and downloaded remotely (Broomfield et al., 2003). 

Telecommunication systems use a hub and spoke network to provide for the movement of electronic data (Campbell and O Kelly 2012). The links are either wired (cables) or wireless. Transmission cost does not increase much with distance traveled. Facilities such as switches, routers, and concentrators are located at the hub to enable communication among a set of nodes, analogous to depots. In relation to a transportation network, the operations, costs, service measures, and constraints are often quite different in a telecom hub network because of the differing natures of objects - freight or passengers versus electronic signals in packets . 

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