scope:

General 

This specification describes the methods to be used to link a Host processor based system with any other similar system or compatible device, in those applications where protocol overheads are to be kept to a minimum.

Experience has shown that the following methods give satisfactory results, although it shall be understood that the protocol does not cover all possible error situations. 3.

Purpose

To ensure that Network Rail's electronic Signalling and Telecommunications Systems can be expected to communicate and interact with each other, a common protocol and message classification needs to be specified. This document builds on past experience and best practice to ensure future compatibility.