net also dates to the turn of the 21st century. More commonly, a combination of fibre and copper is offered to provide fast internet connec- tivity to a subscriber premise. Twisted Pair Copper Wires The use of twisted pair copper wires as a communication medium is as old as telephony. These were developed for the transmission of voice over long distances as determined by the gauge or thickness of the wires. As discussed in Chapter 3, voice signals have frequency components in a range of 300-3400 Hz, which can be supported for telecommunications over distances of tens of kilometres over typical 0.4 or 0.5 mm gauge twisted pair copper wires with sufficiently low loss. Broadband Telecommunications Technologies and Management Figure 9.1 A Novation CAT acoustically coupled modem [4]. Source: Lorax on en.wikipedia (public domain): https://commons.wikimedia.org/wiki/File%3AAcoustic_coupler_20041015_175456_1.jpg Table 9.1 Evolution of modem rates Modem Transmission rate Hayes Smartmodem 300 bps Late 1980s 2.4 kbps Superfax 14400 14.4 kbps Late 1990s 56 kbps Twisted pair copper wire telephone lines have also been used for low rate data communica- tions since the 1920s. Applications have included teleprompters, automated telegraphs and radar-to-air defence systems communications. A later application was in telephony systems using dual-tone multi-frequency signalling for call set-up since the early 1960s. In the 1970s acoustically coupled modems (Figure 9.1) used different audio tones to represent 0 and 1 and transmit data between nascent desktop computers over the voice bandwidth of telephone lines (i.e. 300-3400 H: The maximum transmission rates achieved were in the order of 300 bits per second (bps). Over the next two decades modem technology using the telephone improved and by the end of 1990s dial-up modems were capable of supporting 56 kbps in the downstream. A list of modems and their transmission rates is shown in Table 9.1. All these devices used the same frequency band as that of voice. The full potential of twist