Editorial [Intro to the Special Issue]

The purpose of this special issue is to focus attention on current research and practice in two important and exciting areas of interest to the readers of this TRANSACTIONS. We are very much indebted to the Guest Associate Editors, S.K. Mitra (active) and J.F. Kaiser (digital), who were responsible for the reviews of the manuscripts. Active networks, and in particular active RC networks, have been studied for some time, and many basic and useful results have been obtained and continue to be obtained. The digital-filtering area warrants our serious attention not only because it is now economically feasible to consider the associated special-purpose computertype implementations, but also because it has given rise to many interesting and fundamental problems of a type not ordinarily encountered by the network theoretician.