Sound wrench according to Römer, acoustic stimulus- and reaction apparatus (Kraepelin, Psych. Arb., I, 4). A sensible platiunum contact P is mounted on a membrane of finest veneer wood resp. isinglass, that is opened by very weak sound waves. So the armature of the electric magnet E, which is connected to the same current circuit, is dropping, so that a second current circuit for the chronoscope is opened resp. closed. By pulling a drawcord the armature is relifted. The apparatus is of high sensitivity; by the drop of the armature a small clock serves as an acoustic signal. The movement of the armature is regulated ba the screws S1 and S2, at which the platium points are positioned; 4,100 kg.

Schallschlüssel nach Römer, akustischer Reiz- und Reaktionsapparat (Kraepelin, Psych. Arb., I, 4)