The telecommunication system of Beijing Subway consists of the sub-systems of transmission, wireless equipment, telethons for public affairs, closed circuit television, special-use telephone（including that for dispatching trains and central calling）, broadcast system and clocks, thus forming the comprehensive communication network for service use, sending all kinds of information like voice, words, data and pictures. Not only is it an important means to conduct the operation of subway but also can serve the purpose of preventing disasters, providing aids and dealing with accidents under abnormal circumstances.  

• The transmission subsystem can provide the technological departments within the subway system with reliable and flexible data-transmitting channels. With optic fiber as its transmission media and optical wave as the carrier of information, it can realize a large-volume and long-distance transmission. The transmission system adopts multiple kinds of transmission technology of PDH, SDH and ATM to send voice, data and pictures.  
• The subsystem of wireless telecommunication is a convenient means connecting though -voice the fixed –positioned users within the subway system （dispatching staff at center and different depots on route and the person on duty at the station）and the users in move（train driver and the staff for preventing disasters and repair and maintenance）. For Line 13 and Line Ba-Tong, advanced wireless digital cluster technology is used.  
• The subsystem of telephone for public affairs provides the telephone service both within and outside the subway system.  
• The subsystem of closed circuit television enables the person on duty at the control center and the stations to monitor the stations, station halls, platforms and the entering and leaving of trains. The system monitoring train doors enables the driver to see the opening and closing of the doors of his train.  
• The telephone subsystem for special use includes the telephone for dispatch use and for concentrated use.
  The former, it is the special telecommunication system for exchanging service information between different dispatching systems and other relevant departments.
  The latter, it is the means of telecommunication for the persons on duty at different stations to exchange information with each other.  
• The broadcast subsystem is used by the staff in charge of dispatch at the control center and the persons on duty at the stations so that they can provide the passengers with the information of the operation of trains, safety and guidance and send orders and notices to the working staff. When disasters occur, it can be used by the relevant working staff members to evacuate passengers.  
• The clock subsystem provides the subway system with the synchronized time signals.