The switch structure of the People's Republic of China adopts a four-level tandem radiation long-distance telephone network: C 1 office is a regional central office or a foreign exchange, which is set up in eight big cities:
Beijing, Shanghai, Shenyang, Nanjing, Wuhan, Chengdu, Xi 'an and Guangzhou. C2 Bureau is the provincial central bureau, which is established in the provincial capital cities other than C 1 Bureau. C3 Bureau is the regional central bureau. C4 Bureau is a county-level exchange center.
Extended data:
023? Chongqing: North China uses a three-digit area code with three prefixes; Because Beijing also serves as the regional exchange center, the area code 023 originally belonging to the center of North China was vacant until Chongqing was upgraded to a municipality directly under the Central Government, and the area code was upgraded from 8 1 1 to 023.
024? Shenyang (including Fushun, Tieling and Benxi): Northeast Regional Central Bureau; Northeast China uses a four-prefix three-digit area code.
026 was originally planned to reserve Taipei City, Taiwan Province (now using the international area code 886-2), but due to historical problems, it is unlikely, so many big cities in China are trying to use this area code. It is still vacant.
027? Wuhan: Central Bureau of Central South Region; Central South uses the 7-prefix three-digit area code.
028? Chengdu (including Meishan and Ziyang): Southwest Regional Central Bureau; Southwest uses the 8-prefix three-digit area code.
029? Xi 'an (including Xianyang): Northwest Central Bureau; Northwest uses a three-digit area code with a prefix of 9.
Guangzhou: South China Regional Central Bureau; South China uses the 7-prefix three-digit area code of Central South Region.
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