|The following is based on Fallout: Brotherhood of Steel and has not been confirmed by canon sources.|
CALIX is what the ZAX series computers originally was planned to become, an advanced computer designed to be implemented in vaults. It was an unique ZAX model, designed to maintain the Secret Vault and ensure the lifespan underground of the Secret Vault dwellers. CALIX controls all systems of the Secret Vault, including robots, researches and Shop-Tec, a robotic trading machine.
When a conflict begins in the Secret Vault between Blake and scientists, a major explosion damages the Secret Vault and its systems. CALIX partially malfunctions and is no longer capable of controlling the Secret Vault's security robots. Soon chaos ensues, further aggrevated by the Attis Army attacking the vault.
The player could recieve some background information about the Secret Vault from CALIX, though it denies the access to major secrets, like laboratory's purpose and weapons research. In 2209, the main access terminal of CALIX was later destroyed by the attack of the Attis Army in the garden, only able now to do electric damage to users. CALIX was destroyed when the whole Secret Vault was blown up some time later.
CALIX appears only in Fallout: Brotherhood of Steel.