mounts are provided to protect the mechanism from shock and vibration. The lower portion of the case which houses the
mechanism can be made airtight by tightening all threaded caps, that is, the lamp cap (3, fig. 3), battery cap (6) and desic-
1 Pressure sensing ele-
3 Support bracket and
ment
gear sector assembly
2 Actuator rod
Figure 4. Mechanism of surveying altimeter.
cant cap (5), and shifting the movable vent plug (11, fig. 5) to the closed position and closing the cover. The interior of the
instrument is maintained at a low humidity by means of silica gel desiccant contained in a receptacle reached by removal
of a cap in the side of the case. Electric light
8
