|The following is based on Fallout: Brotherhood of Steel and has not been confirmed by canon sources.|
Welcome to the Vault-Tec computer system. I am CALIX, an automated intelligent construct designed to maintain this facility. I provide a variety of services to ensure your lifespan underground”— CALIX
CALIX is what the ZAX series of computers was originally planned to become, an advanced computer designed to be implemented in vaults. It was a 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, research and Shop-Tec, a robotic trading machine.
When a conflict begins in the Secret Vault between Blake and the 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 aggravated by the Attis Army attacking the vault.
The Initiate could receive 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, now only able to do electrical damage to users. CALIX was destroyed when the Secret Vault was blown up some time later.
CALIX appears only in Fallout: Brotherhood of Steel.