Applications of built-in-test equipment within large systems

The paper surveys the literature on the application of built-in-test equipment (BITE), which has assumed an increasingly important role in the maintenance of sophisticated systems. Despite the relative ease with which some form of BITE can now be added, and the apparently good performance claimed by designers, there are clear indications that BITE has very often failed in practice in its aim of easy maintainability with low-skilled labour. A particular problem is the rate of `false alarms¿ where fault-free units are removed unnecessarily. Indeed, there is evidence that the overall maintenance costs of some systems would have been lower with less sophisticated BITE. This raises the question of whether it is possible to specify in advance an optimum level of BITE within a given design. Such an optimum level has, however, been found very difficult to predict. Conversely, a convincing case can be made for the BITE specification to be developed in an interactive way throughout the course of design, development, commissioning and field operation, in the light of the available technology and of the whole maintenance strategy. Against this background, BITE deployment is seen as at least as much a management problem as a technical one.