A numerical method for determining the envelope curves to a set of Gershgorin circles in a classical Inverse Nyquist Array diagram is presented. The use of these envelope curves reduces the amount of information displayed when computergraphic terminals are used in the design process. This reduction loads to significant savings in core-memory requirements if the computer terminal is of the refresh type and is not fitted with hardware for circular interpolation. In addition, the use of these curves ensures that only relevant design criteria are displayed, thus reducing the total information which is usually presented.