Karl Küpfmüller, 1928: an early time-domain, closed-loop, stability criterion

Abstract

Karl Küpfmüller was a German engineer who worked for eight years during the 1920s at Siemens & Halske in Berlin. During that time he carried out fundamental work on telegraphy and telephony, network theory, and the systems theory of electrical signal transmission. Like his contemporary in the US, Harry Nyquist, he derived fundamental results in information transmission and closed-loop modelling. In contrast to Nyquist, though, his name is not well-known in the English-speaking world. Indeed, little has appeared in English about him or his work – although his pioneering results in systems theory informed later American work, particularly through the contributions of Ernst Guillemin, a prolific writer of highly influential student texts and a great engineering educator at MIT, who was well-acquainted with the ideas of Küpfmüller (and other German electrical engineers)