scope:

Unless otherwise stated, these notes are generally applicable to the Network Rail route relay interlocking typical circuits BRS-SW67 and the supporting 'R' and 'T' series. The control table notation used is in accordance with NR/L2/SIG/11201, Module A5-3, and relay notation with NR/L2/SIG/11201, Module A5-2.

NR/L2/SIG/11201, Module B7, Section 3 laid down the requirements for interlocking controls and specified their tabulation in control tables. The application of the principles and requirements to route setting systems are summarised in NR/L2/SIG/11201, Module B7, Section 7. This module demonstrates how those controls are provided by the use of free-wired circuitry and enables a comparison with other interlocking systems.

Other relay configurations are possible, particularly where it is not necessary to store the state of interlocking functions in the event of a power failure, in which case lock relays can be dispensed with altogether. Examples are given in NR/L2/SIG/11201, Module B7, Figure 21 and NR/L2/SIG/11201, Module B10, Figure10

PURPOSE AND INTRODUCTION

This module forms part of the Signalling Design handbook (SDH: NR/L2/SIG/11201) and is to be read in conjunction with the other modules of the handbook and reference documentation.

This Network Rail standard contains requirements and guidance on signalling engineering applications. The content supports the specific and general requirements described in Railway Group Standards and the Network Rail Signalling Principles Handbook [NR/L2/SIG/30009].

NOTE Where there is a conflict between this standard and a Railway Group Standard or the Network Rail Signalling Principles Handbook [NR/L2/SIG/30009] then this standard shall not take precedence

Decisions made by a competent person should be supported by appropriate evidence or documentation.

NOTE use of designer notes on drawings (see HSE CDM guidance) will generally suffice as may Design Log entries.

Any adoption of alternative solutions requires an assessment commensurate with the significance of the proposed change and which follows the guidance provided by the Common Safety Method for Risk Evaluation and Assessment [CSM-RA]; Network Rail's adopted method for the control of safety risks.