1 Telecommunication networks and digital subscriber lines
1.5 Digital Subscriber Lines

Terminal equipments of xDSL (Digital Subscriber Line) are specially designed to allow better use of the potential of copper in the access network infrastructure. A common feature of these systems is relatively high transmission speed in the order up to tens of Mbit/s. Digital subscriber lines can be classified according to various criteria. One major division is according to a method of transmission to digital transmission connections in:

- baseband (HDSL (High-speed Digital Subscriber Line), SHDSL (Symmetrical High-speed Digital Subscriber Line)),
- modulated band (ADSL2+ (Asymmetrical Digital Subscriber Line), VDSL2 (Very high-speed Digital Subscriber Line) and G.fast) and it can be operated on subscriber lines together with already installed another service operated on the baseband, for example POTS or ISDN-BRA.

In the case of purely metallic solutions of the access network, where the connection to the provider terminating near the main distribution exchanges, can use ADSL, SHDSL and on limited distance also second improved generation ADSL2+ and VDSL. In the case of hybrid optical and metallic access network solutions, where there are facilities at the provider of extended closer to the subscribers can take full advantage of connections ADSL2+ and VDSL2 and G.fast.