The convergence of computing and telecommunications: Cold War to coal trains
Jonathan Aylen, Robert Gwynne · International Journal for the History of Engineering & Technology · 2025
The internet is built on packet switching: small units of information are sent from node to node in a telecommunications system and re-assembled at their destination. Before the internet there were large centralised computer networks based on circuit switching over telephone lines. An end-to-end circuit was kept open for transmission of data. The Total Operations Processing System (TOPS) adopted by British Rail during the mid-1970’s is the apotheosis of an area wide telecoms linked computer network using circuit switching. The shift to computer based control of freight train consignments and operation using TOPS was part of a long history of control and computation on the railways. British Rail used its own telephone networks to run a nationwide hub-and-spoke information system. Signalling staff helped manage the transition to a digital railway with innovations such as multiplexing, modems and desktop computers. The computer hardware and software for TOPS had its origins in American Cold War air defence. Ultimately, a centralised system was vulnerable. Packet switching allowed a decentralised approach to network design. This was a disruptive change in technology. Yet TOPS was adapted to the new distributed architecture using packet switching and remains in use.