Apeks DS4 First Stage:

The demand for air increases as the divers descends. In the maintenance of air supply, the intermediate pressure arises according to the water level. Regarding this dry sealed system hydrostatic pressure, moving on the external sealing diaphragm, being transmitted to the initial diaphragm through the load transmitter. This initial step is utilizing a unique over-balanced diaphragm illustration wherein the intermediate pressure is being supplied to the secondary stage maximizing that is greater than the traditional balanced samples. As a diver descends to deeper level, the result is the maximum air supply performance on whatever depth it reached.

No turret.
4 medium pressure ports 3/8 UNF.
1 high pressure port 7/16 UNF
Dry sealed system for cold water.