Training tool designed for students RTU communication systems course. At issue in access networks widely used DSL technology. Describes the establishment of systems, evolution, theory and practical realization. Used the information from the literature and authors research. The paper provides ADSL performance analysis of the existing copper wire networks. There are also a real signal and the power spectral density examples. The attached reading list includes both books and journal articles, which focus on ideas has had a significant xDSL technology.