Principles of functioning

The no-retour valve C allowed supplying the tank R1 with air compressed. Through the valve S, air goes up in the tank R2 where the interior pressure balances with the exterior pressure thanks to the supple membrane M. When the membrane is horizontal, valve is closed.

During the breathing in, diver inhales air from the tank R2 with the pipe t. That inspiration lowers the membrane and the vave, and the inhaled air is automatically replaced. During the breathing out, air is repressed by the same pipe and escapes by the rubber valve se, nicknamed "beak of duck".