10 



BELL SYSTEM TECHNICAL JOURNAL 



Fig. 14 — von Ardenne-Hartel, 1930 — tube by Leybold's Nachfolger. 



Fig. 15— Dufour oscillograph of 1923." 

 " Dufour, A., Oscillographe Cathodiquc, Eticnne Chiron, Paris, 1923. 



