scope:

These requirements apply to new concentrator systems for use in Network Rail controlled signal boxes and to subsequent modification of these systems. Each requirement statement has been classified and falls into one of the following three categories: (I)

• Mandatory (indicated by '(M)' at the end of the paragraph). Compliance with these requirements is mandatory.

• Desirable (indicated by '(D)' at the end of the paragraph). These are desirable requirements. Where a group of desirable statements are all needed to satisfy a general requirement '(D*)' will be indicated at the end of the paragraph.

• Information (indicated by '(I)' at the end of the paragraph). These are statements intended to provide explanatory notes.

Purpose

This document defines the requirements to be met by a signal box telephone concentrator system.