Computer-based interlocking is

railway signal A railway signal is a visual display device that conveys instructions or provides warning of instructions regarding the driver’s authority to proceed. The driver interprets the signal's indication and acts accordingly. Typically, a signal mi ...

interlocking implemented with

computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...

s, rather than using older technologies such as relays or

mechanics Mechanics (from Ancient Greek: μηχανική, ''mēkhanikḗ'', "of machines") is the area of mathematics and physics concerned with the relationships between force, matter, and motion among physical objects. Forces applied to objec ...

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 Invensys Ltd. was a multinational engineering and information technology company headquartered in London, United Kingdom. It was formed in 1999 through the merger of BTR plc and Siebe plc. It had offices in more than 50 countries and its prod ...

, GEC-General Signal * Mircrolok II * Smartlock * Germany - Alister CBI from Funkwerk IT

Railway Gazette International ''Railway Gazette International'' is a monthly business magazine and news website covering the railway, metro, light rail and tram industries worldwide. Available by annual subscription, the magazine is read in over 140 countries by transport ...

of July 2012, page 18

Interface between different brands

When interfacing different brands of CBI equipment, it may be necessary to use relays of each regime, which are then hardwired from one to the other. This happens in the middle of the

Channel Tunnel The Channel Tunnel (french: Tunnel sous la Manche), also known as the Chunnel, is a railway tunnel that connects Folkestone (Kent, England, UK) with Coquelles ( Hauts-de-France, France) beneath the English Channel at the Strait of Dover ...

where French and British signalling equipment meet.

Competition Rules

Since only some of the major signalling organisations make CBI equipment, 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.

References

Interlocking systems Rail infrastructure {{rail-transport-stub