The significance of nullators, norators and nullors in active-network theory

Although proposed in 1961, the nullator and norator have not been widely used or understood. At first sight these elements appear rather remote from reality, and in this paper an attempt is made to relate them to some practical devices. It is suggested that a nullator-norator pair (nullor) may be regarded as a reasonable idealization of a number of physical devices, but that the nullator and norator, considered individually, cannot be so regarded, and are not physically meaningful. `Controlled-source¿ behaviour can usefully be represented by nullors in conjunction with passive two-terminal elements, and by generalization of the nodal and loop methods of analysis to deal with networks containing nullors, this can result in significant simplification in the analysis of some active networks. Topological methods of solution may also be used. It is concluded that there are no outstanding difficulties involved in incorporating the nullor into the framework of conventional network theory, and that nullors may be useful in the analysis of practical active networks.