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the piston spring. Basically, screwing in the knob (clockwise direc-
tion) increases inhalation resistance, while unscrewing (anti-clock-
wise direction) decreases inhalation resistance.
When designing this regulation system, two seals were planned
to protect the mechanism from water infiltration. These seals, ad-
equately lubricated during the production or maintenance phase,
preserve the mechanism thread from any oxide formation that
could cause or even block rotation of the regulation knob over
time. By doing so, rotation is instead always soft and the resulting
regulation of inhalation effort can be carried out precisely and eas-
ily as the thread regulating the mechanism is, in fact, waterproof.
The adjustable nozzle is positioned inside the valve compartment
and the exiting air, when the mechanism is opening, is sent inside
the mouthpiece, thanks to the particular care taken during the
design phase of the shape and finish of the inner walls and regu-
lator case.
To ensure negative pressure is not too violent inside the body
which could "suck back in" the diaphragm giving rise to free flow
phenomena, the valve unit contains a diaphragm balancing hole.
When the air flow delivered inside the injector and directly to the
mouthpiece is consistent, it generates negative pressure inside
the regulator case due to an increase in air speed. The negative
pressure, called the “Venturi effect” keeps the diaphragm
crushed, considerably reducing the diver’s inhalation effort.
The Venturi effect stops immediately as soon as the diver stops
inhaling; the diaphragm then returns to its normal position and the
lever, pushed by the spring, raises and allows the piston to come
in contact with the nozzle, stopping air passage.
To optimise the Venturi effect, the Master second stage is
equipped with a flow deflector that has two use positions, as
clearly indicated on the “PRE-DIVE” and “DIVE” regulator Venturi
housing mask, where, in the first position, a flow limiter starts
working that is placed on the mouthpiece, which in fact limits the
Venturi effect, preventing the 2nd stage free flow. In the “DIVE”
position, the Venturi effect is instead expressed at its best, by in-
creasing the air flow delivered to the regulator at maximum levels.
� WARNING: remember to always keep the flow deflector
lever in the “PRE-DIVE” position when the regulator is not in use,
otherwise accidental knocking collision, dropping the breathing
apparatus in water, pressing the manual delivery button when
the regulator is not in your mouth or also suddenly removing
the regulator from your mouth could cause free flow, which
could even be violent, with huge air consumption. In the "DIVE"
position, it should only be used underwater and only with the
regulator in your mouth.
By exhaling, the diver increases pressure inside the regulator
case that opens the conical angled release valve with large di-
ameter, allowing air to exit. The exhaust port delivers this air to the
sides of the head and protects the valve from water turbulence
that could open it, when the inner case is not pressurised, caus-
ing flooding.
An important characteristic of the Master 2nd stage is use of a reg-
ulator in cold water (water temperature <10C or < 50°F), an option
that was particularly well finished during the development phase,
thanks to the special design of the valve case on the regulator.
DIVE PRE-DIVE
SECOND STAGES
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