NR SSI8003-100 ISSUE 1 PDF

Introduction

History

In the past SSI controlled Crossings of all types have been implemented using electro-magnetically operated relays, latterly BR930 types, housed in a number of equipment cases located at the trackside. To maintain the operation of the Crossing under power failure conditions a 24 volt battery is provided to drive the relays , the Crossing road lights and, where provided, operate the Barriers.

The approach now taken in the design of the data for Crossings is to maximise the use of data, minimise the relays at the Crossing and input all Crossing functions directly into the Interlocking via TFMs. This achieves certain positive benefits:

• Removes the need for location-to-location multicore cables to bring to the Crossing all functions required for the Crossing control

• Reduces the number of relays required at the trackside including some of the unreliable Timers.