A method for computing the interval of delay values for which adifferential-delay system is stable

A test for determining the interval of delay values for which delay-differential system is asymptotically stable is presented, i.e. an explicit method is given for calculating h*, such that, for 0⩽h⩽h*, a delay-differential system is stable where h is the delay length. Further, it is shown that the system is not asymptotically stable for h=h*. Both retarded and neutral systems are discussed