scope:

Introduction

SSI is an electronic microprocessor based replacement for the electromechanical technology used predominately in existing relay signalling schemes. Savings are achieved by the elimination of signalling relays except track circuit relays and relays required to interface with certain signalling equipment, e.g. point machines and ground frames, and by the replacement of lineside multicore cabling by serial Data Links. As a result, there is a reduction in the size of buildings, in the resources required for planning and installation and a reduced maintenance requirement.

SSI is intended to maintain the appearance and behaviour of current signalling schemes so far as the railway operating staff are concerned and it is therefore designed to interface with a conventional Signaller's Panel and lineside equipment. However, SSI is compatible with IECC, which includes automatic route setting and VDU based displays. This specification describes the connections from the SSI to the IECC network. Other aspects of IECC design are outside the scope of this document.