PoseidoNet

A relic of pre-War times, the PoseidoNet used to be the internal network providing instantaneous communication between various branches of the Poseidon Energy cartel. The network continued to function after the Great War, used by the Enclave (which likely also used it before the war).

It plays a fairly minor role in Fallout 2, but foreshadows the existence and extent of the power of the Enclave.