scope:

INTRODUCTION

Unless otherwise stated, these notes are generally applicable to the Network Rail route relay interlocking typical circuits and their predecessor, BRS-SW67. The control table notation used is in accordance with NR/L2/SIG/11201, Module A18, and relay notation with NR/L2/SIG/11201, Module A19.

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 may be provided by the use of free-wired circuitry. Figures:1 and 2 identify how the standard controls are applied to free-wired interlocking and enables a comparison with the 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.