This is the Artronic computer network that handles all the systems aboard a TARDIS. The systems connected to it include the Navigation Systems, Guidance Systems, Drive Systems, Defense Systems, the Life Support Systems, and even the Emergency Transceiver. With the exception of the Protyon Unit, all of these systems are composed of exitonic (a.k.a. Artronic) Circuitry and connected with fine grey, hair-like interfaces. Lights move up and down these hairs searching for faults. Older Artron Mainframes (like those on a Type 40) use Old High Gallifreyan for their programming code.

Reliability is ensured by having the Fault Locator operate independently of the Mainframe. Security is ensured by requiring Command Codes to make major changes to the programming.