A circuit-switched digital network, similar to X.25. Datakit supports host-to-host connections and EIA-232 connections for terminals, printers, and hosts.
Most of Bell Laboratories is trunked together on Datakit. On top of DK transport service, people run UUCP for electronic mail and dkcu for remote login.
ISN is the version of Datakit supported by AT&T Information Systems. Bell Laboratories in Holmdel, New Jersey, uses ISN for internal data communication.
["Towards a universal data transport system", A. G. Fraser, IEEE Journal on Selected Areas in Communications, SAC-1(5) pp. 803-16, 1983].