Born in 1988 in the Bellcore laboratories, the ADSL technology had been originally developed to enable Video On Demand, yet, despite several pilot projects in the early 1990s, no conclusive results had been achieved. Since 1995, with the expansion of the Internet, conditions in the marketplace changed significantly and a new target was identified for high transmission in the local access network as performed by ADSL, namely fast Internet connections over the PSTN. Accordingly, a second round of ADSL trials had been launched over the period 1996-1998 with the Internet as the killer application, after which operators began to launch commercial services.
The speed range that may be reached through ADSL is between 1.5 and 10 Mbit/s depending on the quality and length of the copper line. Due to these technical requirements, the proportion of lines that can be upgraded with DSL is actually limited: some quote a maximum of 10% of all lines, especially in the US due to the low quality of copper in the local loops.