Engineering-maintenance methods of the calculation xDSL-lines

For ensuring the efficient subscriber access of the customers to broadband infocommunication services (convergence information IT- & telecommunication TT-technology) corresponding to telecommunication facilities, amongst which important place occupies digital subscriber lines (xDSL-x-“any” Digital Subscriber Line). Variety the xDSL-technologies, and in the first place symmetrical on send rate of the messages in opposite directions (SDSL-Symmetrical Digital Subscriber Line), provide the speediest digital subscriber access (the data rate of the exchange given N×64 kbit/s before 2.048 Mbit/s and more) on existing copper loop cable of the local area telephone to network of the general use (PSTN-Public Switched Telephone Network). It´s offered methods of the engineering evaluation at most attainable lengths subscriber SDSL-line with detailed conclusion of the generalized equation of the length. In this paper discussed typical of PSTN´s Interconnection telecommunications network of the Russian Federation and United national communications network of the Ukraine problem estimations criterion quality QoS (Quality of Service) digital communication of xDSL-line on base 5-ball scale MOS (Mean Opinion Score) for ensuring the required spare on noise-immunity NM (Noise Margin).