NR SSI8003-53 ISSUE 6 PDF

Introduction

SSI equipment may be used in association with other computer-based systems to make up an "Integrated Electronic Control Centre" (IECC). This will typically include a VDU-based "Signalling Display System" (SDS) in place of a conventional control/indication Panel, and an "Automatic Route Setting Computer" (ARS) which reduces the Signaller's workload by automating the task of route-setting in all but the most unusual circumstances. These and other systems in the IECC are connected to the SSI Panel Processors via a duplicated signalling communications network within the Control Centre, which allows any device to interrogate any Panel Processor to ascertain the current "State of the Railway" for its Central Interlocking, and to send panel requests which are passed on to the Interlocking MPMs to be processed.

In an IECC installation the SDS handles the tasks of interpreting button sequences (or the VDU-based equivalent) to generate panel requests, and of updating indications in line with the latest "state of the railway". This eliminates all the Panel Processor data with the exception of the Central Interlocking's identity number, and so no data need be entered in the IND & BUT identity files before running the Panel Processor data compiler. The data files can also be left blank, except the PBK file which requires at least a dummy entrance button list to satisfy the compiler's syntax checking (i.e. a "list header" specifying zero sets of data, followed by an "end of special"). In some circumstances it may be desirable to produce some conventional Panel Processor data to allow testing of Interlocking data on a Design Workstation independently of the SDS. There is no need to delete this data before programming EPROMs for use in the final system, as the extra information is simply ignored by the IECC version of the Panel Processor program. There are differences between this Panel Processor data and that prepared for a Panel controlled Central Interlocking, and this is covered by Section 7.

Most of the Interlocking data in the SSI Central Interlockings in an IECC scheme is identical to that provided for use with a conventional Panel, but there are some additional latches required to provide locking associated with "reminder devices" which are the VDU equivalent of a collar placed on a button on a conventional Panel, and "ARS sub-areas" which allow the Signaller to specify the parts of the controlled area over which automatic route-setting is to operate. The data associated with these latches is described in Sections 2 and 3 respectively.

Like SSI, both the SDS and ARS systems make use of geographic data, which are described in separate documents. To allow communication between the systems to be established, the ARS & SDS data preparation systems access the SSI data identity files to allow them to interpret the SSI "state of the railway" memory, and this requires that a standard nomenclature must be followed for the naming of certain identities. These conventions are described in Section 4.

Other systems in the IECC system also interpret the SSI "state of the railway" memory, and thus any changes made to identity files that are not implemented in all IECC systems simultaneously can lead to mismatches between SSI and IECC. Additionally SSI PFM and PRR files are used in ARS data preparation, and thus any changes to these files may also affect ARS data. Guidance on making these changes is given in Section 5.

Where an SSI scheme makes use of a conventional Control Panel, a crude level of ARS capability can be provided by data within the Interlocking. This is limited by the information available within the "state of the railway memory", and cannot take account of train descriptions and timetable information, but is adequate for simple functions such as automatic terminal platform working. An example of this is described in Section 6.