scope:

Signalling equipment that is replaced or renewed on a like for like basis under corrective maintenance, temporary design as a result of an incident or engineering works and minor signalling renewals that do not affect the application logic of the system or, the controls of the system that have previously been tested to signal orks testing.

Purpose 

This document contains the index to the Signal Maintenance Testing (NR/SMTH)The SMTH provides a maintenance testing regime for the replacement or installation of signalling equipment that does not affect the application logic of the system or, the controls of the system that have previously been tested to signal works testing