Computer-based interlocking

Computer Based Interlocking is the general term for a railway signalling interlocking implemented with computers rather than the older technologies such as relays or mechanics.

General

CBIs are mostly implemented in two parts; a section that implements the safety and failsafe requirements, and a second section that implements "non-vital" controls and indications.

Brands

Different manufacturers have their own brands of CBI such as

• SSI (Solid State Interlocking) - BR, Invensys, GEC-General Signal

• Mircrolok II

Competition Rules

Since only some of the major signalling organisations make CBI equiment, it was agreed that to prevent other players being left out in the cold, CBI equipment would be made available to those players at cost.