public charging networks

A public data network (PDN) is a network established and operated by a telecommunications administration, or a recognized private operating agency, for the specific purpose of providing data transmission services for the public.
The first public packet switching networks were RETD in Spain (1972), the experimental RCP network in France (1972) and Telenet in the United States (1975). "Public data network" was the common name given to the collection of X.25 providers, the first of which were Telenet in the U.S. and DATAPAC in Canada (both in 1976), and Transpac in France (in 1978). The International Packet Switched Service (IPSS) was the first commercial and international packet-switched network (1978). The networks were interconnected with gateways using X.75. These combined networks had large global coverage during the 1980s and into the 1990s. The networks later provided the infrastructure for the early Internet.

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