Hydrostatic valve
The hydrostatic valve prevents squeeze (compression due to increased ambient pressure) of the breathing circuit and is opened following quick changes in depth, or when the diver holds his breath while making a descent of more than 1 metre.
Note: WARNING! To avoid the influence of the hydrostatic valve on the acoustic signature, the diver must ensure that it does not automatically open near the mine, i.e. all descents are made at a safe distance from the mine, and all movements to and from the mine must be made at a constant depth.