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. Moving the lever 180 degrees moved one end of the spring, the other end was loosely attached to the shutter blade. After exposure the spring could be set for the next exposure by moving the lever in the opposite direction, without moving the shutter blade. The T setting remained. The shutter, then, could be tensioned in either of its two positions. 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.

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.