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Access Technologies Access is arguably the most important part of the network infrastructure, since it is the point at which all revenue-generating customers come into contact with the network. It is also an area of great diversity from basic telephone access through private exchange and Automatic Call Distributor (ACD) connections, not to mention HFC cable Integrated Access Device (IAD) protocol stack TV, to leased data service connections and wireless connectivity in the form of wireless Local Area Networks (LANs) and of course the now near ubiquitous mobile phone (in Europe at least) | Next Generation Network Services Neill Wilkinson Copyright 2002 John Wiley Sons Ltd ISBNs 0-471-48667-1 Hardback 0-470-84603-8 Electronic 6 Access Technologies INTRODUCTION Access is arguably the most important part of the network infrastructure since it is the point at which all revenue-generating customers come into contact with the network. It is also an area of great diversity from basic telephone access through private exchange and Automatic Call Distributor ACD connections not to mention HFC cable Integrated Access Device IAD protocol stack TV to leased data service connections and wireless connectivity in the form of wireless Local Area Networks LANs and of course the now near ubiquitous mobile phone in Europe at least . The one major advancement that is without doubt the greatest improvement in both functionality for the customer and revenue generation from the network operators perspective is the introduction of xDSL technologies that have increased the capacity of the humble copper pair of cables in the local loop. This has also created major ramifications across the world with the unbundling of the local loop via regulatory control causing severe pain to the incumbent telecoms operators. This chapter covers the area that has undergone as much change in its history as the change to the core networks that this book discusses. The invention of the telephone by Bell as discussed in the Preface started the access infrastructure from the four and two-wire circuit carrying analogue voice to the capabilities of xDSL. Co-axial cables and fibre optics have seen an increase in the data carrying capacity of the local loop from a few hundred bits per second to the thousands of megabits per second capability of fibre optic cables. The increase in capacity is what is allowing the increase in the complexity of services that can be offered from the core of the network and has allowed the proliferation of the Internet model of intelligent endpoints. 86 ACCESS .