Chronometric node

A chronometric node was a device implanted into every Borg drone, designed to precisely record the passage of time.

''In an alternate 2390, The Doctor, working with Chakotay and Harry Kim, was able to access Seven of Nine's chronometric node and pinpoint her exact time of death in 2375. This allowed the team to determine the exact point in time to send a message to Seven's interplexing beacon, utilizing a Borg temporal transmitter. Sending Seven a new set of phase corrections for the quantum slipstream Voyager was utilizing in an attempt to return to the Alpha Quadrant, they were successful in collapsing the slipstream and returning the ship to normal space, changing history and saving Voyager from destruction.''