nd relatively inexpensive. Furthermore, they can transport the electrical signals representing voice for very long distances with small loss. Broadband Telecommunications Technologies and Management J.T.B. DEL Figure 3.1 Bell's telephone [2]. Source: Illustrated London News - published 1872 (cited: http:// hwdp1.blogspot.com.au/) As noted above, early telephony technological enhancements focused on the development of better wires as well as better microphones and speakers in order that voice signals may be transported over long distances and with good quality. Another major research focus was the development of switches, through which many subscribers could be connected to each other at low infrastructure costs. Switching Two telephones need to be connected by wires (circuits) which carry the electrical signals bet- ween them. Although the connection can be direct, it is generally made through one or more intermediary switches. These switches are located in a telephone exchange, as illustrated in Figure 3.2. Switching was an important initial step in the development of telephony services as it made the roll out of large networks economically feasible. The importance of switches was already well known from telegraph roll-outs as messages between cities were relayed through major hubs: direct connections between every two cities with dedicated lines necessitated a very large network and was impractical. The difference is Voice Communications Local exchange Twisted pair copper wires Figure 3.2 A telephone call connected through a local exchange Figure 3.3 Switching efficiency illustrated in Figure 3.3: a central hub enables 5 nodes to be connected to each other using 5 links, whereas one-to-one direct connections require a total of 10 lines. Furthermore, the length of individual connections can be prohibitive. A central switch reduces the number of required links, as well as the total length, to be proportional to the number of subscribers (N) whereas full connectivity requires links proportional to N2 [precisely it