One limiting factor is the viewing Angle, which is comparable to using a camera lens: a telephoto lens has a narrower view than a wide-angle lens.
限制因素之一就是观察角度，这与使用照相机的情况类似：长焦镜头的视野比广角镜头的观察角度要窄得多。
2
Suitable for casement window, hanging on the window (in conjunction with the hinge), for limiting the opening Angle of the sash.
适用于平开窗、上悬窗(与铰链配合使用)，用于限制窗扇开启角度。
3
The Anglelimiting apparatus comprises an arched plate, a trough-shaped plate, an orienting plate, a transverse bolt and a transverse bolt positioning plate.