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A public land mobile network (PLMN), as defined in telecommunications regulation, is a network that is established and operated by an administration or by a recognized operating agency (ROA) for the specific purpose of providing land mobile telecommunications services to the public. A PLMN is identified by the Mobile Country Code (MCC) and the Mobile Network Code (MNC). Each operator providing mobile services has its own PLMN. PLMNs interconnect with other PLMNs and Public switched telephone networks (PSTN) for telephone communications or with internet service providers for data and internet access of which links are defined as interconnect links between providers. These links mostly incorporate SDH digital transmission networks via fiber optic on land and digital microwave links. Access to PLMN services is achieved by means of an ''air interface'' involving radio communications between mobile phones or other wireless enabled user equipment and land-based radio transmitters or radio base stations or even fiber optic distributed SDH network between mobile base stations and central stations via SDH equipment (ADMs) with integrated IP network services. ==Public switched telephone network== (詳細はPublic Switched Telephone Network (PSTN) in order to route calls. The PSTN is the world's collection of interconnected voice-oriented public telephone networks, in much the same way that the Internet is the concatenation of the world's public IP-based packet-switched networks. It is both commercially- and government-owned. This aggregation of circuit-switching telephone networks has evolved greatly from the days of Alexander Graham Bell, and in the late 20th century became almost entirely digital in nature — except for the final link from the central (local) telephone office to the user (the local loop). It also extends into mobile as well as fixed telephones. The PSTN also furnishes much of the Internet's long-distance infrastructure and, for the majority of users, the access network as well. Because Internet Service Providers (ISPs) pay the long-distance carriers for access to their infrastructure, and share the circuits among many users through packet switching, the end Internet user avoids having to pay usage tolls to anyone other than their ISP. The PSTN is largely governed by technical standards created by the ITU-T, and uses E.163/E.164 addresses (usually called telephone numbers) for addressing. A number of large private telephone networks are not connected to the PSTN, and are used for military purposes (such as the Defense Switched Network). There are also private networks run by large companies that are linked to the PSTN, but only through controlled gateways such as private branch exchanges. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Public land mobile network」の詳細全文を読む スポンサード リンク
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