An asymmetric digital subscriber line (ADSL) is a digital communication technology that allows rapid data transfer along standard telephone lines. An ADSL socket can refer either to the cable connection point on a computer or wireless networking hub or to the filter socket that is required to split signals received through a telephone line into voice calls and data transfer signals. ADSL technology achieves faster speeds than those provided by standard modem connections by utilizing unused frequencies in the telephone line to accelerate package transfers.
In reference to direct computer connections and wireless networking hub connections, an ADSL socket is the port into which an ADSL data cable is plugged. The ADSL cable can transfer the data by extending the telephone wire connection between a wall socket and the receiving device. An ADSL cable can also be used to connect directly between an ADSL output port on a wireless networking hub and an ADSL socket on a computer if required.
As the technology utilizes unused frequencies on a standard telephone line for data transfer, a splitter, or filtering ADSL socket, needs to be installed directly at the telephone wall connection point. A voice line will pick up all frequencies on a line and therefore will also pick up interference from the data signals if this filter is not installed. Filter sockets are generally provided free of charge by an Internet service provider (ISP), but additional sockets can be purchased if required. It is generally recommended that a filtering ADSL socket be used for each voice telephone connection in a house to filter out data frequency interference.
The filtering ADSL socket is a single input to dual output splitter device that contains a simple low-pass frequency filter in the voice line output socket. This filter removes the data frequencies from the voice line but allows all frequencies to pass through to the ADSL cable connection. A digital subscriber line (DSL) device — such as a wireless hub — is designed to filter out low frequencies from the received signal, and therefore, no microfiltering device is required on this output.
Other DSL services exist, but ADSL is the most commonly used type of home connection. An ADSL connection is most suited to home use due to the increased bandwidth that is provided in the receiving, or downloading, direction in comparison to the outgoing, or uploading, signal. This mismatch in bandwidths provides the asymmetrical characteristic noted in the technology’s name. Business users often require higher upload speeds and will therefore need to invest in a more balanced DSL service or pay for a leased telephone line.