The local cable network (cable plant) is a part of public switched telephone network (PSTN) which connects local telephone exchanges with customer’s premises equipment (CPE). It is built up of multipair twisted cables. Cable pairs are twisted to avoid mutual influence (crosstalks) among the pairs. Cable construction is developed for transmission of voice frequencies and it remains almost the same for some decades. This cable plant works well for telephone transmission even if all cable pairs are active. In the eightees ISDN technology appeared which transmitted signals up to 60 kHz and soon it became clear that only 70 % to 80 % of cable pairs met technical requirements for this technology. The main obstacle was mutual influence among pairs (crosstalks) which increases with frequency. Next came another transmission technologies as HDSL, ADSL, SHDSL, which were designed to connect PBX exchsnges to the PSTN and to deliver Internet to the customer’s home. All these technologies are called xDSL. Nowadays some new technologies appear, but the principles and line codes are the same (2B 1Q, PAM-16, DMT). In general, transmission of signals with frequencies up to 1 MHz over local telephone lines is quite common now. Technologies up to 2 MHz or even 8 MHz (over short lines) are coming soon. Most widespread is the ADSL service, so it is important for operator company to make evaluation of practically achievable penetration of ADSL service over existing local cable plant [1].