DSL provides simultaneous voice and high-speed data services over a single pair of copper wires. DSL technology allows data transmission at speeds much faster than the best available analog and digital modems. There are several variations of the DSL products that use copper cabling to move data between the end subscriber and the host location. Data is separated from voice traffic at the serving central office and then connected to a high-speed data network and delivered to the host destination.
Different applications require a variety of speeds in order to transmit data.
Therefore, DSL based services offer the appropriate amount of bandwidth to the user for his or her specific application. There are multiple line coding techniques used by the DSL vendors. Each of these techniques has strengths and weaknesses within a telephony network. Some DSL technology is intended for use in campus environments and others work well within a building. Technology for telephony must be compliant with certain standards to prevent interference and cross talk.