micrometer in this optical system is arranged so that movement of the micrometer screw brings the
opposite sides of the circle into optical coincidence with the amount of movement read on the
micrometer. Shifting the changeover knob on the side of the instrument allows either the vertical or
horizontal circle to be read from the single microscope eyepiece. The vertical circle has a coincidence-
type level.
Figure 3-4. Wild T-3 Precision Theodolite
EN0593
3-16
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