Electronic organ loudness control - changes from constant to piano forte loudness by turning flat bar on wedge diaphragm spring

摘要

In an electronic organ, a change from piano-forte playing (with variable loudness) to constant loudness can be effected mechanically so that troublesome key contacts are eliminated. The key T carries a light barrier Sp. When a light spring F1 has been deflected, a stronger spring F2 with a wedge opening in a diaphragm B is moved. This admits a varying light flux L from a light source S to a photocell so that piano-forte playing is possible. Turning the flat bar U depresses the spring F2 so that now the barrier Sp opens the light passage suddenly and the organ plays with a constant volume of sound.