LED30P helps at night works, mining site or long distance works so on.
Because LED lights indicate where the prism is by flashing.
It's easy to change the brightness and frequency by switching the button at back side of prism target.

Selction of Brightness: 100%, 70%, 40%, 20%
Frequency of Flashing: 1hz, 3hz, 6hz, and lighting

When setting as prism constant 0, it must use with the attached adapter LA-0.