History of Digital Subscriber Line

Digital subscriber line technology was developed by Joe Lechleider at Bellcore (later renamed Telcordia Technologies). The first type of DSL, ADSL (Asymmetric Digital Subscriber Line) was created in 1988, through placing digital signals above the baseband analog voice signal used to carry out phone conversations.

US phone companies will promote DSL to compete with cable internet service. The first DSL services were provided through a dry loop, but once the Federal Communications Commission (FCC) made it mandatory for incumbent local exchange carriers share their lines with competing providers such as Verizon, the shared line became very common. This system allows for a single pair to transmit information with a DSLAM, and analog voice (phone conversion), at the same time.

Earlier ADSL standards were able to deliver 8 Mbit/s to the user over roughly 2km of ethernet cables (unshielded twisted pair copper wire). With the newest ADSL standard (ADSL2+), it is possible to deliver up to 24 Mbit/s, based on the distance from the DSLAM (usually located at the providers offices). Many customers are unfortunate, and further away from the provider than 2KM, which will result in reduced data transfer rates.