SUMMARYAs is well known, computer-aided design methods that make use of specific properties of the networks being solved are much more efficient than general approaches suitable for very large classes of problems. In this paper an approach to acceptability regions, grounded on the bilinear theorem convenient for linear networks, is studied. Thanks to the bilinearity, exact analytical solutions on first-order linear manifolds in the parameter space, i.e. when only one parameter is being changed at time, are available. This so-called one-dimensional orthogonal search (ODOS) has been applied to a segment approximation of acceptability regions. This approach leads to spectacular results concerning shapes of acceptability regions, applicable in fundamental design problems.