198811 – Williams – Adelaide Signalling Project: Solid State Interlocking

Solid State Interlockings (SSI) is a microprocessor based system, designed for use in railway signalling installations to compute and execute the signalling interlocking functions in a safe and reliable manner. The development of SSI was undertaken jointly by British Rail, GEC General Signal Company Limited and Westinghouse Signals Limited in the United Kingdom. British Rai has been responsible for the basic design of hardware and software, safety validation and for overall project management. GEC and Westinghouse Signals have translated the British Rail design concepts into fully engineered production equipment.

The objectives of the development were to use microprocessors to reduce the cost of railway signalling installations without changing the way that the operators and drivers view a signalling system.