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ADSL

The bandwidth of the humble telephone line is not restricted by the copper lines, so much as the electronic filtering that occurs at the exchange. These were designed to minimise interference and optimise the bandwidth for voice levels. Modem designers have had to work within these restrictions on standard lines and by clever utilisation of combined frequency and amplitude modulation have been able to cram the above data exchange rates into the normal voice range.

The emergence of Asymmetric Digital Subscriber Line (ADSL) as a force for the provision of broadband style services has highlighted how good the telephone lines are if the filtering is bypassed. However there is a problem with much Australian telephony distribution hardware. The lines have been installed with an eye to economy and the bandwidth capabilities have already been partly utilised by using single lines to carry two separate subscribers traffic. This use of a single line to service a pair of customers prohibits easy installation of broadband services, as they require a completely separate line from subscriber to exchange to function properly. This paired installation is all too common and a major impediment to broadband via telephone lines in many areas.

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