Command neural interface
From Halopedia, the Halo wiki
Summary
Neural lace implants are implanted in the brains of every UNSC officer upon conscription. Once installed, they cannot be removed without killing the host, and are permanent. Their main use is the storage of data codes, NAV data, and also for receiving telemetry from outside sources. AIs can access the lace with the owner's consent, and retrieve data for use.
In the level Keyes, the Master Chief recovers the CNI transponder from the body of Captain Keyes, whose Flood-infested form had to be killed to retrieve them.
