Backup systems is an upgrade used by both GDI and Nod during the Ascension Conflict.
The concept of the Backup Systems originated from the Mammoth Mk. II's experimental self-repair system. After the AW-12 Mastodon entered service, GDI engineers revamped the old concept and installed nanotech repair modules derived from Nod technology into the Mastodons. The backup module will activate upon catastrophic system failure and will begin to slowly repair the disabled Mastodon; given enough time to rewire and repair the failed systems, the Mastodon husk can be brought back online without assistance from an engineer.
The introduction of this feature revolutionized battlefield repairs, and Nod engineers soon copied this feature, installing Backup Systems on their own Avatars.
With this upgrade, husks from heavy units will regain health over time. When the husk is at full HP, the unit comes back online at 50% HP. Husks can be destroyed or captured before this happens so they must be protected.
Units that leave husks are: the Mammoth tank, Mastodon and Rhino for GDI. And the Nod Widow, Avatar and Aftershock.
It is important to note that this upgrade comes from the Offense Class. And can therefore only be applied to the Rhino and Aftershock, both Defense Class units, if the player has already purchased the upgrade with a Tier 3 Offense Crawler.