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Heart Diagnosis by Means of Electrical Auscultation
Some time ago, Dr. Leo Jacobsohn of Berlin reported a method of electrical amplification of the heart sounds in man, so that they may be heard by persons even at great distances. As amplifiers, the same cathode tubes were used that are employed in radio apparatus. The radio station at Berlin has transmitted heart sounds 850 kilometers. The subject was in the reception room of the transmitting station, and Swiss physicians at Davos were able to distinguish clearly the rhythm of the heart, but not the more delicate heart sounds. A few days ago, Dr. Jacobsohn demonstrated an American improvement of the procedure. The method makes use of the tone filters described by Geheimrat Wagner, and which already play an important part in modern telephony. They separate several conversations that pass over the same wire at the same time. The filters let through
BERLIN. JAMA. 1926;86(2):133-134. doi:10.1001/jama.1926.02670280053026