A public character-switching/packet-switching network operated by British Telecom.

A public packet-switching network operated by McDonnell Douglas Network Systems Company.

Tymnet was an international data communications network headquartered in San Jose, California that utilized virtual call packet switched technology and used X.25, SNA/SDLC, ASCII and BSC interfaces to connect host computers (servers)at thousands of large companies, educational institutions, and government agencies. Users typically connected via dial-up connections or dedicated async connections. The business consisted of a large public network that supported dial-up users and a private network business that allowed government agencies and large companies (mostly banks and airlines) to build their own dedicated networks.