The opposite side of the moving surface is provided with a single absolute type optical rule and two groups of read heads.

以及在该运动台面的相对侧设有单支的绝对式光学尺及两组读头。

youdao

2 projecting heads for table cinematographs, 1 optical sound head, 1 carbon arc projection lamp, 1 slide projector and more. All untested.

2个放映机头，用于桌式电影摄影机，1个电子光声头，1台煤油弧光灯，1个滑线电阻，1台幻灯机，1个印片机箱，1个暗房照明灯(煤油)，均未检测。

youdao

The team is already thinking of applications for metamaterials as read-heads for future generations of hard-disk drives or optical modulators for communications.

ECONOMIST: MONITOR