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Single-pair high-speed digital subscriber lines (SHDSL) enable regular telephone lines to connect to the Internet and convey data streams over a single pair of copper wires. It is also known as a symmetric digital subscriber line. SHDSL is the first system to be developed from scratch and approved by the International Telecommunication Union (ITU) to be an international standard in symmetric digital subscriber lines (DSL). It was developed to enhance other existing DSL technologies, such as the single-line digital subscriber line (SDSL) and the asymmetric digital subscriber line (ADSL). Generally, it is capable of transferring T1, E1, ATM, IP, and ISDN signals at a high-speed data rate that ranges between 192 kilobits per second (Kbps) and 2.3 megabits per second (Mbps), and covers distances from 1.8 to 4.6 miles (about 3 to 7.5 km) per second.
A user with a data rate requirement higher than what an SHDSL can provide may use more than one copper pair to convey data from the source to the destination. Once on the receiving end, the data are recombined from the lines used to transport them. This technique is known as bonding or inverse multiplexing.
SHDSL is commonly used in homes to access the Internet for gaming, telephony, music and video uploads and downloads, e-mailing, messaging, website browsing, and other social, educational, business, and personal purposes. Small and medium enterprises use it for video conferencing, web hosting, remote local area network (LAN) access, corporate LAN-to-LAN connections, virtual private networking, and file transfers involving large volume of data. The bandwidth or the size of the information highway can be dynamically allocated among voice, data, and video applications since the services are handled within the digital field.
The basic requirements to secure SHDSL service is a subscription with an Internet service provider (ISP). A telephone line must also be furnished for the dedicated use of the service, which means that the telephone line cannot function as telephone service and an SHDSL service at the same time, even if a frequency splitter is installed. An SHDSL modem will also be needed for the service to connect the computer to the ISP using the telephone line. Also, an SHDSL router would be needed for computers that are connected to a network.