The Advent of HDSLThe telephone companies saw the realities. They had mile after mile of copper cable, they knew the logistical and cost ramifications of fiber limited its deployment, and they recognized the flaws of repeatered T1/E1. So they started looking for a better way, and in the late 1980's the collective research arm of the Bell operating companies, Bellcore, devised a new method.They called the concept High-bit-rate Digital Subscriber Line (HDSL). Its intent was straightforward: to deliver a high-performance and cost-effective way of transmitting at speeds of up to 2 mbps over existing copper cable, a way that was adaptable, faster and precluded the need for repeaters or special line conditioning. HDSL leverages the huge amount of existing copper cable, delivering a streamlined alternative to the installation of competing solutions. Initially, deployment of HDSL was slow, and it was used by engineers to provide T1/E12 links on the more difficult and potentially more complex routes. As prices improved, HDSL implementation has become the fastest and most cost-competitive method of establishing T1/E1 links on copper for public and private networks. Just as importantly, HDSL's adaptive capabilities provide a level of signal quality comparable to a fiber optic link, and services can be turned up in hours instead of weeks or months.
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