The first form of this shutter, fitted to the N&G Universals, consists of an arc shaped segment with a cut-out. To set the shutter the segment is drawn over the lens opening against a spring coiled around a rod. The bottom of the rod forms the piston of the pneumatic delay. This very simple arrangement was not self-capping. If the shutter was released at its slowest speed with a short pressure the shutter blade was caught with the aperture over the lens giving a T setting.

In 1906 the shutter was modified for the Sibyl range of cameras. The spring and rod were replaced by a coiled spring and lever. The sector moves across the lens at uniform speed in alternate directions and can be tensioned in either position. The main spring fits over a spindle on the setting sector, its two ends are both at the bottom of the spindle and project forming arms that lie each side of a shaped projection. The shutter is tensioned when an external lever moves one of the arms through a short arc. As the arm is moved the setting sector is held by the release lever. Pressing the release lever frees the sector allowing it to rotate, and the blade to move across the lens opening. On the earliest and some later models the setting lever was below and to one side of the lens. Later it was over the pivot of the blade. On most models there is a + and - sign on the shutter blade indicating in which direction the setting-lever should be moved. The shutter is particularly quiet in operation.

In 1912 the shutter was improved by the inclusion of an I, B, T setting.

The sector shutter remained in production until around 1940, variations exist dependent on the camera.

The image on the far right shows the I, B, T selector to the left of the lens. The power spring fits over the upright rod where the blades pivot, the ends of the spring fit each side of the rod to which the piston of the delay cylinder is attached. The setting-lever (part of the housing) sits between the ends of the spring.