As a result of the increasing complexity of communication systems there is a need for a level of system knowledge among staff at each site that cannot easily be met. If some percentage of this knowledge can be formalised as an expert system, it can be used as a support tool and 'expert advisor' for system operators. The paper presents the Satellite Communications Network Expert (SaNE), a knowledge-based aid designed to provide engineering support for fault diagnosis. The SaNE is composed of two elements: a satcom network model, which simulates the structure and functionality of a system based loosely upon a large military satcom network, and a diagnostic component, which uses knowledge- and model-based reasoning techniques to analyse system anomalies and diagnose possible causes for the alarms such networks generate. The development cycle is described, emphasising lessons learnt during development and testing and the advantages and disadvantages of the techniques applied. The goal of the SaNE project is primarily commercial acceptance rather than innovation. It is the aim of this paper to illustrate how novel concepts can be implemented in a practical system without compromising this goal.
