6
DIN or INT connection
SCUBAPRO fi rst stages are available with different tank valve connections:
DIN :
uses a threaded connection
complying with ISO 12209-2
norm (200 or 300 bars).
YOKE (INT):
this international
connection is composed of a
yoke and screw and can be
used up to 230 bars, according
to the ISO norm.
NITROX (EN 144-3):
this
connection uses a threaded
wheel complying with EN 144-3
norm and can be used only with
oxygen enriched air mixes (Nitrox)
with an oxygen concentration
from 22 to 100% at a maximum
working pressure of 200 bar.
Img. 3
5.2 Second
Stages
Balanced system
Balancing the pressure forces acting within the demand valve allows the use of a much lighter spring
load decreasing the inhalation resistance and providing a smoother breathing second stage.
Diver adjustable inhalation resistance control
Second stages equipped with this system have an over-sized external control knob acting
directly on the spring tension (Img. 1, point 9), allowing the diver to adjust the inhalation
resistance in order to adapt it to the needs of the dive conditions. Adjusting the control
knob (clockwise rotation) causes an increase in inhalation resistance. Adjusting with a
counterclockwise rotation reduces the spring tension for lower inhalation effort. All depends
on the diving conditions, such as in strong currents, when the diver spends some time with
his head down and when the second stage is used as an alternate air source (octopus).
!
WARNING
A higher inhalation resistance does not necessarily imply a lower air consumption,
in fact it may even have the opposite effect, due to the higher effort required to
trigger the air fl ow increasing your work of breathing.
V.I.V.A. (patented)
V.I.V.A. is the acronym for “Venturi Initiated Vacuum Assist.” High speed air fl ow passing
over the vane creates a low pressure area inside the second stage housing. This depression
pulls the diaphragm inside the housing, maintaining pressure on the valve lever and keeping
the valve open without requiring an additional effort on the part of the diver. On some
SCUBAPRO second stages the Venturi effect (V.I.V.A.) can be adjusted during the dive by
changing the position of the fl ow vane via the knob positioned on the outside of the second
stage. On SCUBAPRO second stages not equipped with an external knob, the V.I.V.A. vane
position is preset to ensure maximum performance and prevent free-fl ow, but it can be
adjusted at any time by a SCUBAPRO Authorized service technician.
