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1.6 SPIROGUIDE ELECTRONICS PACKAGE INCLUDING BAC, HUD AND
DDU
The SpiroGuide electronics package consists of:
• Breathing Apparatus Computer (BAC)
• Digital Display Unit (DDU)
• Wireless Heads-Up Display (HUD)
The BAC is a computer unit and pressure sensor mounted in the backplate. It is
powered by 6 AA batteries.
The wireless HUD is a combination pressure gauge and electronic low air warning
device. It also indicates PASS Pre-Alert mode and PASS Alarm mode. The HUD is
installed in the face mask.
The BAC and HUD will link together based on an address code received from each
other. The BAC and HUD to be used together must linked before use, following the
procedure in section 2.7. When the BAC is started it will only connect to the HUD it
previously has been linked to.
The HUD includes a light sensor to measure the ambient light. The brightness of the
LEDs is automatically adjusted according to the ambient light conditions. The pressure
indication displayed in the HUD is refreshed every 2 seconds. The HUD is powered
with 2 AAA batteries.
The DDU is located on the left shoulder with the mechanical pressure gauge and
mechanical whistle. The DDU is connected with a cable to the BAC. It is powered
from the BAC and has no batteries.
The motion sensor for the integrated PASS and the sensor for measuring absorbed
temperature are both located in the display unit.
The BAC, HUD and DDU activates when the SCBA cylinder valve is opened.
1.7 AUDIBLE AND VISUAL LOW AIR WARNINGS
The S9 and S9 Incurve is equipped with dual redundant low air warning End of
Service Time (EOST) indicators.
The primary low air alarm (EOST) is an audible mechanical whistle. The secondary
alarms (EOST) indicators are visual ashing yellow and red LED’s on the HUD.
Audible Warning and Pressure Gauge
When the primary air supply pressure has dropped to approximately 33 % the
audible alarm will start to sound. An analog pressure gauge is located along with
the audible mechanical whistle on the left shoulder in front of the user. An optional
secondary audible electronic low air warning is available. The sounders for the
electronic low air alarm, when activated, are located on both sides of the BAC. The
electronic low air warning also has an optional mutable function depending of the
preference of the Fire Department. If mutable, the electronic low air warning will be
silenced for 10 seconds by pressing the backlight button on the DDU (see section
3.2).
The DDU pressure gauge is a secondary pressure gauge.
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