Purpose: General purpose switching and muting, LCD back-lighting, supply line switching circuits.
用途： 用于一般静音开关，液晶显示器的背景照明，线性开关电源。
2
Frequently it has a hinged glass cover to hold copy flat, and may have a removable section in which a transparency holder can be positioned for back-lighting illumination.
一般都备有铰链着的玻璃盖面，以把稿件夹平。有些更可以换上透明片架，在后面打灯照明。
3
Shooting someone in front of a window during the day can present bad back-lighting problems—the camera will expose for the bright window, leaving your subject underexposed and lost in shadow.