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Can you list the top facts and stats about Public switched telephone network?
Summarize this article for a 10 years old
The public switched telephone network (PSTN) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telecommunication. The network consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables interconnected by switching centers, such as central offices, network tandems, and international gateways, which allow telephone users to communicate with each other.
The technical operation of the PSTN adheres to the standards internationally promulgated by the ITU-T. These standards have their origins in the development of local telephone networks, primarily in the Bell System in the United States and in the networks of European ITU members. The E.163 and E.164 standards provide a single global address space in the form of telephone numbers. The combination of the interconnected networks and a global telephone numbering plan allows telephones around the world to connect with each other.