NGN services, such as VoIP, and all managed services, including MOD and VPN.  We currently have intelligent networks installed over our public switched telephone networks for our domestic long distance  and international networks, as well as a local intelligent network in the Taipei, Taichung and Kaohsiung metropolitan areas. Our  intelligent network is designed to facilitate the use of value-added services by providing more information about calls and allowing  greater management of those calls.  As of December 31, 2011, our domestic network included 17.6 million installed telephone lines, and reached virtually all  homes and businesses in Taiwan.  International network.  Our international transmission infrastructure consists of both submarine cable and satellite  transmission systems, which link our national network directly to 101 telecommunications service providers in 45 international  destinations.  International calls are routed between Taiwan and international destinations through one of our two international switching  centers, one located in Taipei and the other in Kaohsiung. Each center had two time-division multiplexing, or TDM, international  gateway switches and two NGN international gateway switch. We had a trunk capacity of 143,040 channels in total as of December  31, 2011.  As of December 31, 2011, we have invested in 16 submarine cables, seven of which land in Taiwan. After the number of  submarine cables we invest in has increased from 14 in 2010 to 16 in 2011, we have increased the capacity of each of our current  submarine cables, increasing our aggregate total capacity from 774 Gbps in 2010 to 1,058 Gbps in 2011. Mobile Services Network  Our mobile services network consists of:  ●  cell sites, which are physical locations equipped with a base station consisting of transmitters, receivers and other equipment  used to communicate through radio channels with customers’ mobile handsets within the range of a cell;  ●  BSC (base station controllers) for GSM or RNC (radio network controller) for 3G, which connect to, and control , the base  station within each cell site;  ●  cellular switching service centers, which control the base station controllers and the processing and routing of telephone calls;  ●  GGSN (gateway GPRS support nodes), which connect our GPRS network to the internet;  ●  SGSN (serving GPRS support nodes), which connect the GPRS network to the base station controllers; and  ●  transmission lines, which link (i) with respect to the GSM or 3G network, the mobile switching service centers, base station  controllers, base stations and the public switched telephone network, and (ii) with respect to the GPRS network, the base  station controllers, the support nodes and the internet.  The following table sets forth selected information regarding our mobile networks as of the dates indicated.  As of December 31, 2009 2010 2011 GSM system GSM base stations 9,384 9,336 9,531  Switches 49 44 44 Lines of capacity (in thousands) 7,700 6,500 6,500  Taiwan population coverage 99.9% 99.9% 99.9% P AR T I 44