ABSTRACTAlternating current isographs, representing the terms of a polynomial by variation of the time phase of a.c. generator outputs have not attracted much attention in recent years. In this paper we shall describe an isograph based on this principle, and which is capable of solving seventh degree equations having real coefficients. The instrument as constructed can also be used for the deliniation of the frequency response of passive and active networks and by a curve fitting process, for network synthesis.