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).