ADSL is an acronym stands for Asymmetric Digital Subscriber Line. It is a type of digital subscriber line (DSL) technology which is used for data communication. It provides faster data communication over copper telephone lines rather than a conventional voice band modem.
ADSL is different from less common symmetric digital subscriber line because it provides greater bandwidth towards the customer end than the upstream. This is why it is called asymmetric. This is also a reason behind its fast speed.
ADSL uses a special filter called micro filter and installs it on subscriber's telephone line. It allows both ADSL and telephone services to be used at the same time. This is why it is faster than SDSL.
A special type of model called ADSL modem is required to receive ADSL service. Subscribers must be within close geographical locations to the provider's central office. Typically this distance is within a radius of 2 to 2.5 miles.
ADSL supports data rates of from 1.5 to 9 Mbps while receiving data (also known as the downstream rate) and from 16 to 640 Kbps while sending data (also known as the upstream rate).