scope:

Purpose and Scope

The purpose is to: 

• list all amendments to SSI design documents SSI8003 "SSI Data Preparation" and SSI8500 "Design of SSI Signalling Schemes"

• to advise which of these may need to be applied retrospectively to existing SSI signalling schemes

• to give guidance in identifying whether these have been applied to existing SSI signalling schemes

Also included for completeness are any on-site SSI programs issues, linked to the above, that may also need to be installed retrospectively.

The scope is limited as follows:

• This document is intended for use by those engineers experienced in the application of SSI. Sections 1 to 5 are also intended for use by persons with some signalling knowledge although assistance may be required from more experienced engineers.

• The Amendments listed include all changes made to SSI design documents SSI8003 since February 1989, and SSI8500 since May 1990, up to those included in the SSI Applications Manual as defined in Issue Two of RT/E/S/17002.

• Amendments listed as "Retrospective" comprise those where SSISPG has identified that retrospective action may need to be taken. This is generally limited to retrospection arising out of deficiencies in published scheme design or data - it does not cover retrospection arising out of changes to Signalling Standards or where earlier unpublished scheme design or data does not match that subsequently issued in SSI8003 or SSI8500.

• Guidance is given on the symptoms of any problems addressed by Retrospective Amendments and on how to recognise whether approved solutions have been applied, but deciding whether retrospective action needs to be taken is outside the scope of this document.