scope:

This document covers the philosophy of automated control by computer systems or programme machines but does not consider manual based control systems such as the older signal boxes with levers or with push-buttons.

It is not the purpose of this document to describe in technology specific terms how the philosophy is to be met. Reference should be made to the signalling control systems codes of practice relating to computer systems and programme machines (G2521 and G2501) for this level of detail.

Purpose 

This document is intended to indicate the underlying philosophy that must be adopted when preparing and introducing signalling control systems to London Underground.