some cases, COs are connected by the directly. Such possibility is shown by the dotted lines for three COs connected to the TEIII. COs may be directly connected with the toll exchange. This option is shown by the dotted line for the COII1. Automatic Branch Exchange (PABX) is served by the nearest CO. All TEs are forming the meshed network. Up to the 1990s, TE was independent element of the local network. Operators did not use the equipment combined functions Tandem and Toll Exchanges. So, TE provided connections between COs of the local network, and access to the toll exchange. A function of the toll exchange is to establish connections for the long-distance and international calls. Last type of calls is served by the Gateway (GW). Processing of the local calls is performed by the COs and TEs. If a subscriber dials digit "8" (prefix of the long-distance connection in the national PSTN) all further processing of the call is a function of a toll exchange. The numbering plan for the cellular networks based on the Area Code (three digits) and number of mobile terminal (seven digits). In this case, the Area Code defines the concrete cellular network. Mobile phone There are four mobile phone service brands that cover all Russia: Beeline, MegaFon, Mobile TeleSystems and Tele2. At the end of 2013 there were about 239 million SIM cards in use in the country, which is equal to 168% of the population. The access points (AP) are built in long-distance telephone exchanges (LDTEs), Russian fixed-line communication infrastructure which is present in every province. As a result, interconnecting mobile operator only needs to create "last kilometer" circuits to the regional LDTE, the requirement already imposed by its mobile license. Rostelecom, the leading fixed-line operator in the country has regional subsidiaries who provide cellular services. In May 2008, 3G network was deployed in St. Petersburg, in Kazan in June of that year, and in Sochi in July of that year. By 2010, 3G networks covered largely most of Russia. In April 2011, MegaFon deployed high-definition voice services on its Moscow and Sochi GSM and UMTS networks. As the key supplier of core and access networks to MegaFon, Nokia Siemens Networks was responsible for the HD voice implementation, which is also a world first for a commercial GSM network. In early 2011, Rostelecom signed a memorandum of understanding with the three main MNOs