NR SSI8003-52 ISSUE 8 PDF

Introduction

Unlike a Route Relay Interlocking which can be expanded to include however many relays are required to carry out a particular task, each Solid State Interlocking has a finite capacity which cannot be exceeded. When the capacity of a single SSI Central Interlocking is exceeded, the controlled area shall be subdivided between a number of Interlockings. There are three major limitations on the capacity of a Central Interlocking:

• The number of TFMs which can be connected.

• The memory capacity of the MPMs & PPMs.

• The processing speed of the MPMs & PPMs.