ISC APECS Quick start guide

APECS™ OPERATIONAL
INSTRUCTIONS
(v. 2.7)
10 July 2008
©2008 InnerSpace Systems Corp. All rights reserved. Distribution limited to
owners and users of ISC Closed Circuit Rebreathers. See paragraph “DOCUMENT
REPRODUCTION AND LICENSING” for specifics.

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DOCUMENT REPRODUCTION AND LICENSING
©2008 InnerSpace Systems Corp (ISC). All rights reserved. Distribution is intended for owners of the
APECS™ electronics system. Viewers of the electronic version of this documentation may not reproduce
electronically, on any media, nor in hard copy, in part or in whole without express written permission of ISC.
Owners of rebreather equipment featuring these electronic systems are hereby licensed to no more than
one electronic copy, one backup media copy, and one hard copy of this document intended for their
operational service of the referenced equipment. The latest revision electronic form of this document is
maintained on the ISC website for review at: http://www.customrebreathers.com. Electronic access via the
Internet is limited to referencing the ISC website. This is intended to eliminate the possibility of propagation
of out of date copies of the documentation.
Conventions
The various menus, commands and other screen information described in this
manual are CAPS BOLD and truncated just as they appear on the actual menu
screens for the sake of clarity. Conditions that could affect the safety of the diver
are called out in RED BOLD to facilitate proper warning of potentially hazardous
conditions. Closed Circuit Rebreathers artificially manipulate the divers breathing
environment which creates the potential for injury and death if the apparatus is
not properly assembled, tested, and calibrated. Divers certified on previous
releases of APECS™ are strongly advised to study this manual carefully and
consult with an ISC approved instructor prior to using this release.
Introduction
The ISC Advanced Personal Environmental Controller System (APECS™) is a
family of CCR electronics designed to be used in a variety of diving roles to fit the
operational needs of the end user. The APECS™ family is designed to be used
in saturation, military, and recreational roles providing reliable, user friendly
operation with room for ISC factory customization to further meet the end users
needs. The APECS™ has a simple self intuitive menu and confirm system and
essential information dive screen that minimizes the task loading of the diver by
providing a “quick look” ability of essential information and the ability to quickly
change on the fly operational changes to the breathing media. Version 2.7 is the
latest general release of the software and consolidates the features of 2.5 into a
common core with four unique configurations to simplify software maintenance.
Version 2.7 is also designed to accommodate the addition of an Isolator Board
which facilitates integration of third party decompression computers onto the
breathing loop.

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Basic
Functions/Features
•Simple self intuitive two button menu and confirm system.
•Independent isolated display system with pressure/gas resistant cabling.
•Independent pressure/water proofed primary and secondary electronics and
power supplies.
•Jaksa power efficient automatic oxygen addition system. (Operational time
is dependant on diver’s use of backlight, ambient temperature, battery
make, age of battery, and diver use.). Using the Alkaline AA battery packs,
experience varies with the Primary, usually 25-50 hours, then for the
secondary subsystem at 50-100 operational hours.
•Average PO2 window. (Bold annotation on display)
•Tertiary redundant oxygen sensor system
•3 sensor independent window.
•Voting logic automatic oxygen addition system.
•Voting logic indicator. Indicates what specific sensor is out of tolerance at
that moment. (A sensor that may become disconnected or completely fail,
the APECS™ will still average and maintain the current set point.)
•Current set point window.
•Breathing loop temp. (Monitors breathing loop temp that the diver is
breathing)
•Ambient water temp.
•Set points selectable on the fly: Manual mode (0.20), 0.5, 0.7, 1.0, 1.1, 1.2,
1.3, 1.4, and ASP.
•Bilinear 2 point calibration system. (For accurate high and low point PO2
information).
•High Altitude Oxygen Sensor Calibration (Both Metric [meters] and Imperial
[feet] altitudes).
•Sensor MV indicator. (Gives sensor output (Millivolts) on the fly to the diver
in real time. This will indicate to the diver the health of the sensors and
voting logic validation).
•Low battery indicators. LOW BATT annotation will appear blinking at 5.2
volts, with the auto disabling of the display backlight further indicating to the
diver a low power situation for the primary electronics system.
•BATTERY no-load/load indicator. (Indicates to the diver the health of the
power supply while under a load from the solenoid)
•BACK LIGHT enable/disable option.
•KEEP BACK LITE ON enable/disable option
•DISPLAY POWER option enable/disable option
•System status: It is the heart beat indicating to the diver that the electronics
have not locked up and are functioning.

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•Selectable
oxygen dosage. May be adjusted on the fly to allow user to set to personal
settings according to work effort and depth of dive, this may be used to
minimize oxygen spikes. This is accomplished in two ways, by the Adaptive
Injection Algorithm which controls the amount of time the solenoid is open
and by the user selectable oxygen off time menu which increments in
intervals of 4, 5, 6, 7, and 8 seconds off.
•No wet sensors.
•Two minute start up timeout for calibration, and altitude PO2 adjustment.
The Megalodon strengths come from a practical approach based off of designer
experience and the application of design principles that closely follows function
leading to form. Regarding the functions of the APECS™ electronics, it is
encouraged that the diver feels free to punch the buttons on the handsets to
see what they do, starting with the Menu/Confirm buttons.
DANGER! The Megalodon operates by using batteries, the diver must
insure that the batteries are fresh enough to conduct the planned diving
operation or the batteries must be replaced if they are in question on
reliability. Also, the power switches must be turned on prior to the diving
operation. The extreme Maximum allowed supply voltage is 10.0 volts,
and minimum voltage is 5.2 under load volts See pre dive check sheet.
Software System Configurations
The APECS 2.7 software comes in four configurations, each specific for the
targeted use of the electronics. These are:
•SOLHUD – Solenoid and HUD controller on one board – used when an
Isolator board is installed to support the OEM Shearwater Pursuit dive
computer or other approved external dive computers in the future. This
software version allows the electronics board to support both the oxygen
injection solenoid and the heads up display.
•SOL – Solenoid controller, also known as the Primary Controller. This is
the traditional setpoint controller.
•HUD – Heads Up controller, also known as the Secondary Controller. This
is the traditional HUD controller software.
•COPIS – The COPIS 2.70 software version is very similar to the HUD
version. It sports the water temperature support as its primary difference
from that of the HUD controller, along with, of course, a name change
displaying COPIS 2.70.
These various software items are appropriately loaded to the electronics
module at time of manufacture for the intended use of the APECS 2.7
Megalodon head assembly.

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APECS™
Operating Instructions
Power on the battery box power switches inside the Megalodon head lid. Notice
on the handsets the opening screen to both the Primary and Secondary
displays. The opening screen is the ISC logo with the version of electronics and
description of the individual display.
Primary Handset
The main operational page screen will be the diver’s primary information on the
current status based on operational priorities. In bold letters will be AVG. The
AVG is the average PO2 based off of the 3 sensors and the voting logic
system. The AVG is what you want to observe primarily for decompression
reasons and to see how close you are to your desired set point. Below the bold
AVG is S1, S2, and S3, each sensor is depicted so the diver may observe
sensor status. The diver at any time may observe an inverse video around one
of the depicted sensors, if this is observed, the voting logic is voting out the
sensor and continuing the averaging of the two remaining sensors. The
APECS™ will self correct if the problem is temporary, if the sensor has failed or
connection is broken the diver must abort the dive and exit the water as soon
as possible observing both displays and being prepared to conduct an
immediate action procedure (IAP).
System Status Indicator: The SSI is the “heart beat” of the APECS™ and is
indicating the operational status of the electronics, the heartbeat (- & | +
characters) is visible on every screen. The main page (PO2 Display) has an
additional indicator (*) which when present indicates the solenoid is firing (the
diver should also be able to hear the solenoid fire).
WARNING! If for any reason the diver observes one single character
instead of changing characters the APECS™ has “Locked up” and the
primary system operating the solenoid has failed, the diver will have to use
the secondary display / HUD to fly the Meg manually and the diver must
exit the water as soon as possible and use IAP when necessary.
MENU/CONFIRM: Press the Menu button of the primary hand set and scroll
through the menu options, the diver will see the following; CHANGE SP?
SYSTEM MONITOR, TEMPERATURE, OXY INJECT, BL ENBL/DISBL, KEEP
BACKLITE ON, DISPLAY POWERSAVE, METRIC/IMPERIAL, CALIBRATE,
SET OXYGEN PERCENT, ALTITUDE, MAX SET POINT. Two minutes after
power on the METRIC/IMPERIAL, CALIBRATE, SET OXYGEN PERCENT and
ALTITUDE menus will be unavailable. The diver may select an option from the

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menu and press the
CONFIRM button and see the option lock into place into a submenu or some
operational information the diver may want to see.
WARNING! It is imperative that the diver NOT enter the water within two
minutes of power on to avoid the inadvertent selection of inappropriate
options.
The Diver at any time may leave the selected option by making a selected
operational change to the APECS™ or the system will time out in 5 seconds and
go back to the main diving informational screen.
WARNING! Always insure that you have a breathable P02 in the loop, and
set point that will also support your planned decompression.
CHANGE SP?: Set point selection is accessed from this option by pushing the
MENU button to “CHANGE SP?” Push the CONFIRM button to lock in the
option. The diver will see the first of the set points that can be locked in with the
CONFIRM button. The first set point is MAN. Man stands for manual. The
manual set point is an artificial set point of 0.20 and attempts to maintain a loop
PO2 of .20 (Air) at all times. The desired use is for swimming pool training,
surface swimming while breathing on the loop to avoid hypoxia, and for pre-
diving the Megalodon to avoid wasting oxygen through solenoid injection.
Set Points: The diver has the following set points that may be set on the fly
during the dive, or preset prior to entering the water; MAN, 0.5, 0.7, 1.0, 1.1, 1.2,
1.3, 1.4, and ASP. ASP stands for Auto Set Point. Auto Set Point is designed to
be used during rapid descents. ASP is normally selected immediately prior to
descent; as the diver descends and PO2 rises, ASP ensures that the PO2 does
not fall below current PO2 at any point. Once the descent is complete the diver
should select a fixed set point. The diver can select the maximum PO2 that ASP
will maintain on the SET MAX SET POINT menu.
WARNING! The diver must ensure that they have a breathable PO2 at all
times and maintain the planned PO2 to support the planned
decompression.
Other considerations are Oxygen CNS toxicity and Whole body Oxygen
toxicity, the planned PO2 must insure that all oxygen hazards are avoided by
prudent CCR diving practices. So use the oxygen set points wisely.
SYSTEM MONITOR: The second menu option after the CHANGE SP selection
is the SYSTEM MONITOR. The SYSTEM MONITOR page is the diagnoses

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page for the
Megalodon. The diver may access SYSTEM MONITOR during the dive to
monitor the sensor mv (sensor millivolts) and the BATTERY: NORM and LOAD
voltages (LOAD voltage on primary handset only). The NORM battery indicator
shows the drop in voltage when there is no load on the battery. The LOAD
reading is the battery load for when the solenoid is activating and putting a strain
on the battery, it is this indicator that the diver needs to be aware of for battery
performance.
WARNING! The lower limit is 5.2 volts and the diver must replace the
battery!
The maximum battery voltage indication is 10.0 volts. Early low battery
indicators are the failure of the backlight to turn on when a button is pushed to
see the display in low light conditions, a second indicator is the LOW BATT
indicator flashing on the primary handset main page and on the BL ENABLE
page, the KEEP BACKLITE ON setting will be ignored in this state. The LOW
BATT warning is triggered by a LOAD voltage of 5.2v or less, if the LOAD
voltage rises above 5.2v when the solenoid is not firing the LOW BATT indicator
will display only while the solenoid is firing, in both cases the back light is
disabled and will not be available until the system power is reset. If the primary
battery voltage should drop below ~4.5v the handset display will “go blank”, the
processor will continue to operate, however the solenoid will cease “firing”. If this
occurs, the diver will need to reference the secondary display and HUD to “fly”
the system manually.
DANGER! If the system is configured with an Isolation board and third
party electronics, voltage below ~4.5v will cause the handset to “go blank”,
the solenoid will cease firing and the HUD will cease to work. PO2 must be
monitored on the third party system.
DANGER! Terminate the dive as soon as practical considering
decompression and other operational factors. Both conditions warrant the
battery to be replaced prior to the next dive!
In most diving scenarios, the diver has adequate time to exit the water without
sacrificing safety.
The sensor mv is an indicator of sensor degradation (health), the diver may see
how the sensor is performing at all times during the pre-dive, dive, and post-dive,
operations. The diver should record the information on the pre-dive/post-dive
check sheet to monitor sensor life and performance over time. Normal sensor
mv is 8 to 13.5 in air at sea level, 25°c. Sensor mv output will be less at higher

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elevations and or
lower temperatures. It is a prudent habit to record the sensor mv at various set
points during the dive and to do comparison check on later dives.
TEMPERATURE: The temperature sensors monitor the ambient water or air
temperature and the breathing loop temperature on the primary handset and the
loop temperature only on the secondary handset.
BL ENBL/DISBL: The back light may be disabled at any time by the diver and
maintain that setting for as long as the diver wishes. To disable the backlight the
diver must access the option to BL ENBL/DISBL and push the menu button to
ENABLE or DISABLE and push the CONFIRM button to lock in the selection.
NOTE: The back light low battery indicator will also be disabled if the BL
DISBL option is selected.
KEEP BACKLITE ON: This option will force the back light to remain illuminated
continuously while the system is powered on. It is ignored in the event of a low
battery condition as described above and if the option is enabled the DISPLAY
POWERSAVE option will be ignored. This options defaults to disabled anytime
the system power is cycled.
DISPLAY POWERSAVE: When enabled under normal operating conditions
(KEEP BACKLITE ON / DISABLED) the handset unit will “go blank” after ten
minutes of inactivity (no button pushes), this has no effect on the CPU or
solenoid operation. This option is ignored if KEEP BACKLITE ON is set to
ENABLE.
With the above three options the diver has great flexibility with which to manage
power and handset readability.
OXY INJECT: The OXY INJECT setting is the means to adjust the oxygen
injection by setting the timeout intervals. The possible “off time” (duration of time
the solenoid will not “fire”) settings are 4,5,6,7 and 8 seconds. The purpose of
controlling the required off time between solenoid “firing” is to allow time for the
oxygen in the loop to homogenize to help avoid spikes in PO2 and to facilitate
the operation of the Adaptive Injection Algorithm. The duration of time the
solenoid is permitted to “fire” is controlled by the Adaptive Injection Algorithm
(AIA). The Adaptive Injection Algorithm monitors the current PO2 and adjusts
the permitted “firing” time to maintain the desired set point as determined by ASP
(current set point on descent) or set via the CHANGE SP menu. The permitted
solenoid “firing” durations range between a .25 second and 4 seconds depending
on the rate of response of current PO2 vs. desired PO2.

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WARNING! It is the diver’s responsibility to monitor and maintain a safe
PO2 at all times, and to monitor the rate of change of PO2 especially during
times of high workload, descents and ascents! COMPLANCY KILLS!
The APECS™ Primary and Secondary display will time out of all menus
automatically after five seconds of in-activity and also fall asleep in surface or
dive mode after approximately ten minutes (if DISPLAY POWERSAVE is
enabled) to save power but will act as a sentinel monitoring the operating
systems. At anytime below or above the water both displays may be accessed
by pushing any button on the display desired as long as the power supplies are
on. It is very convenient to push the out board buttons on handsets to quickly
access the first menu page for PO2 status.
Settings: The APECS™ may be configured for CALIBRATION,
IMPERIAL/METRIC, SET OXYGEN PERCENT and ALTITUDE settings. These
menus may only be accessed within a two minute time frame from turning the
power on during the pre dive procedures; this is to prevent the diver from
creating a hazardous condition during the dive. At anytime during the pre dive
the diver may reset the two minute window by turning the power off and turning
the power on again. These menus are common to both the primary and
secondary systems and will be discussed at the end of this manual.
Warning: At no time should the diver enter the water within the two minute
time frame of turning the power on.
Secondary Handset (APECS Configurations)
The APECS secondary handset shares the same simple two button
MENU/CONFIRM system as the primary handset. The secondary handset is
totally isolated from the primary system in regards to information, power supplies,
and calibration. The only commonality between the primary handset and the
secondary handset are the sensors, each displaying the sensor output. The
secondary and the primary handsets are truly isolated and independent from
each other. It has been shown that a severed hand set cable (bare wires in salt
water) on operational dives did not affect the other handset, (in this case the
primary handset system).
Note: The secondary handset does not operate the solenoid in any way. The sole
purpose for the secondary is to provide a proper isolated independent backup
measuring the loop PO2 in the case of a primary system failure. The diver may
operate the Megalodon manually by manually injecting oxygen into the breathing

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loop to maintain a
manually fixed set point based off of the planned diving operation.
The secondary hand set displays the average PO2, individual sensor outputs,
and the SYSTEM MONITOR (heart beat) along with the ISC logo. The
secondary has the following menu options; MAIN, SYSTEM MONITOR,
TEMPERATURE, BL ENBL/DISBL, HUD ENBLE/DISBLE/TEST, HUD
BRIGHTNESS, KEEP BACKLITE ON, DISPLAY POWERSAVE,
METRIC/IMPERIAL, CALIBRATE, SET OXYGEN PERCENTAGE, and
ALITIUDE.
The diver may scroll through the menus and access the menu options the same
way as with the primary hand set. The diver will notice one difference in the
SYSTEM MONITOR in that the NORM battery voltage only is displayed and not
the LOAD voltage. The secondary does not operate the solenoid. The operation
of the MAIN, SYSTEM MONITOR, BL ENBL/DISBL, KEEP BACKLITE ON, and
DISPLAY POWER SAVE menus are as described above for the primary
handset.
TEMPERATURE: The TEMPERATURE screen displays only loop temperature
as the loop sensor is located in the head. The water temperature sensor is
located in the primary handset.

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HUD Operation
The HUD is only available on the secondary hand set system of a dual APECS
system or on the Primay handset on a Shearwater configuration; it displays the 3
individual sensors by color and number of blinks. The diver may at any time turn
off the HUD especially after the dive to save battery power and may turn it back
on at any time.
Note: If the HUD is disabled and the PO2 falls below .5 the HUD will
automatically enable until such time as the PO2 rises above .5 at which time it
will automatically disable.
The HUD brightness may also be adjusted to bright and dim. The dim may be
used for when there is no ambient light and the bright may be too bright. The
dim does not save any more power as the bright; in fact it uses more power.
The HUD is a powerful indicator to you and your buddy or student, at any time
the buddy/instructor can see what you/buddy/student are breathing and the
condition of each sensor by looking at the color and number of blinks.
The following is a brief explanation of the HUD color and number system (single
LED HUD).
Color PO2 Blinks Condition
Red <0.50 Rapid Blink Preliminary alert to a HYPOXIC loop.
Red 0.5 5 Short Ambient air.
Red 0.6 4 Short
Red 0.7 3 Short
Red 0.9 1 Short
Orange 1.0 1 Short Post calibration on O2
Green 1.1 1 Short
Green 1.2 2 Short
Green 1.3 3 Short
Green 1.4 4 Short
Green >1.5 Rapid Blink Preliminary alert to HYPEROXIC loop.
Example: During the dive the diver has a set point of 1.2, the diver will observe
the following on the HUD, Sensor 1, green blink blink, pause, Sensor 2, green
blink blink, pause, Sensor 3, green blink blink, long pause and back to Sensor
one again.
Note: The system is very simple and is more complex to explain then to interpret.

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DUAL LED HUD: The dual LED configuration features two LEDs oriented
approximately 90 degrees apart to facilitate divers with various degrees of color
blindness. The upper LED is dedicated green and the lower LED is dedicated
Red. The blinking pattern is identical to the table above with the exception of a
PO2 of 1.0 will cause both the red and green LEDs to blink instead of one LED
blinking orange.
METRIC/IMPERIAL: The METRIC/IMPERIAL menu allows the diver to choose
between metric and imperial units of measurement. This screen is only available
for the first two minutes after power on. Care should be taken that both the
primary and secondary system are set to the same setting to avoid calibration
problems.
Calibration Procedures
The APECS™ is a two point calibration system with high altitude oxygen sensor
adjustment. It is imperative that both the MAXIMUM OXYGEN and ALTITUDE
are properly set prior to calibration. This system allows the diver to set the PO2
level based on the diver’s altitude zone at time of calibration, the altitude ceiling
is 14,700 feet (4,481m) at PO2 of 0.12 ata. The APECS™ also has a sensor
millivolt output indicator displaying on both handsets during high point calibration
procedures to aid the diver in a proper loop flush. The first point of calibration is
ambient air and the second point is maximum oxygen. To best perform the
calibration procedure follow the pre dive check sheet and these instructions.
When you select the calibration menu the first screen also displays the
percentage of oxygen used for the highpoint and the altitude used for calibration.
This will normally be 100% and 000 when used with pure oxygen and the Head
Only Calibration Kit at sea level. Ensure this is set correctly, it may be adjusted
via the SET OXYGEN PERCENTAGE menu.
SET OXYGEN PERCENTAGE: Adds the ability of selecting the calibration
oxygen quality percentage from 70-100%. This allows the user to safely use
oxygen of limited purity. This selection, like CALIBRATE, is only available within
the first two minutes after powering on the system. It is available on both the
primary and secondary systems. To enter the oxygen quality menu, depress the
MENU button until the “SET OXYGEN PERCENT” is displayed. It displays the
current percentage the system has in its menu from recent or previous settings of
this entry. Selecting the CONFIRM button enters this function. The user can
decrement the current percentage to the next lower percentage, having a range
from 70% to 100%. Stepping beyond 100 decreases the percentage in
increments of one percent per button push i.e. 99, 98, 97 etc. There is a feature
of the switch hits called a long switch which is used for making large changes in

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the percentage. A
long switch is holding the switch for greater than two seconds. The MENU long
switch has the effect here of subtracting ten percent from the current setting,
allowing the user quicker setting of the desired oxygen percentage. We
recommend watching the “heartbeat” character in the lower right corner of the
display screen for the third character change, indicating approximately three
seconds have passed, before releasing the switch to decrement by ten percent.
This oxygen percentage is only used during the CALIBRATE mode to provide
proper parameters for the determination of the mathematical formula later used
in displaying the setpoint of each oxygen sensor during operation (i.e. sensor
millivolt output vs. PO2 display calculations). It is highly recommended that the
diver use an oxygen analyzer to determine the quality of the oxygen in the O2
cylinder used during calibration.
KNOW YOUR OXYGEN QUALITY!
One question frequently asked is “Will the oxygen percentage affect my PO2
during the dive?” The answer is no. Once breathing from the loop, the partial
pressure of oxygen in the mix you are breathing will be maintained at the
selected set point by the electronics and is appropriately displayed on the
handsets and HUD as that PO2. A low oxygen percentage results in more of the
oxygen gas mix to be used up faster since the other gasses are treated as part of
the diluent gas. The oxygen percentage setting is only used during calibration.
The diver doesn’t need to recalibrate for each oxygen percentage change when
changing oxygen sources.
WARNING! IF THE OXYGEN PERCENTAGE IS SET INCORRECTLY THE
UNIT WILL NOT CALIBRATE CORRECTLY RESULTING IN A POTENTIALLY
LETHAL CONDITION!
The MAXIMUM OXYGEN set point submenu has new checks to attempt to
prevent the user from selecting the maximum O2 while the sensors are still
exposed to ambient air. The effect is the CONFIRM switch is ignored until the
system reads a millivolt reading on all three sensors exceeding 20 mv. Pushing
the confirm button several times with no action should alert the user to read the
millivolt output readings on that page of the display to determine that the oxygen
level is not high enough for the HiPO2 point. Many users have accidentally hit
the confirm button for the air point calibration too many times and resulted in
having to restart the entire calibration procedure needlessly. ISC recommends
the user become familiar with the millivolt readings of the three oxygen sensors
at various PO2s (in air, calibration gas, and at depth) to familiarize the healthy
outputs of the sensors for later real-time analysis during a dive of the health of a
suspected bad sensor. Becoming familiar with the normal voltage readings of

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each sensor at the
normal set point used will assist in analyzing sensor behavior and add another
tool for potential problem analysis during a dive, should the need arise, and
during sensor calibration.
Next it is essential to ensure that the altitude is set correctly to provide accurate
data for calibration. The calibration altitude can be seen on the CALIBRATE
menu screen. If the diver needs to change the altitude it is accomplished by
means of the ALTITUDE menu. Altitude calibration is accomplished by utilizing
zones. Altitude selection is only used to affect the calibration adjustments and
only needs to be set prior to calibration if the altitude has changed.
Altitude zone selections: The altitude submenu section of the sensor calibration
has been enhanced to provide a High PO2 limit. ISC has implemented an
ambient air PO2 for the low point calibration along with the Maximum O2 PO2 for
the high point. The oxygen quality percentage is used to adjust the new high
point PO2 to properly represent the calibration maximum oxygen PO2 for the
selected altitude zone. This adjusted low and high point is displayed on the
altitude menu during calibration and changes with each altitude zone selection.
Altitude Zone selections during sensor calibration of both the primary and
secondary subsystems are accomplished as follows:
1. Enter ALTITUDE menu within two minutes of power on.
2. Answer CONFIRM to “ARE YOU SURE?” and “ARE YOU REALLY
SURE?”. CALIBRATE ALTITUDE submenu is displayed.
3. Initial display shows “Current PO2 = .21”. This is the current setting as
last calibrated.
4. Prompt line initially asks > 000 FT and shows = (the current
PO2)….(current MAX OXYGEN setting) i.e. .21 …. 100.
5. The MENU button becomes SELECT in this submenu. SELECT
increments to the next altitude zone. The bottom point in the zone
represents the HiPO2 result as just described.
Example, 100%O2, altitude is 6,500 feet. LoPO2=0.17, HiPO2=0.81 (.77x1.00).
The altitude menu calculates the high point PO2 to be the HiPo2 at 100% oxygen
times the oxygen percentage currently set in the MAX OXYGEN menu and
displays the result as the HiPo2 as the diver selects the appropriate altitude
zone.

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Revision NEW APECS™ 2.7 14 of 19
Date: 10 July 2008
APECS ™ OPERATIONAL
INSTRUCTIONS (v. 2.7)
The following table illustrates the permissible altitude zones.
Altitude Zone in
FEET (Meters)
LoPO2
in AIR
HiPO2
at 100%
Oxygen
> 0 (0) 0.21 0.99
> 1,200 (380) 0.20 0.96
> 2,700 (840) 0.19 0.90
> 4,200 (1300) 0.18 0.86
> 5,700 (1750) 0.17 0.81
> 7,200 (2210) 0.16 0.76
> 9,000 (2740) 0.15 0.71
> 10,700 (3280) 0.14 0.67
> 12,700 (3890) 0.13 0.62
> 14,700 (4500) 0.12 0.57
Selecting the CONFIRM button at this point locks in the selected altitude zone for
this calibration, and displays ALTITUDE SAVED then returns to the main screen.
Once the altitude is set and the O2 percentage has been correctly selected, the
user can then proceed with calibration.
Once calibrated, the breathing mix PO2s should properly display regardless of
current altitude.
WARNING! Prior to accomplishing the low point calibration the diver
should remove the sensor carriage lid and ensure the sensors are properly
aired in ambient air.
During the pre dive check of the Megalodon the checklist will tell you to conduct
the air point calibration. After turning the power on, the diver will scroll through
the primary and secondary handsets menu and push the confirm button when the
option is found. On the primary and secondary handsets you will see the
following after selecting the calibration option: CALIBRATE, and above that, it
will ask “ARE YOU REALLY SURE?” You will see a YES or NO and you may
push yes to go on or no to cancel. At this point of calibration you have just
completed the calibration for air and the two minute time out is on hold for you to
complete the next phase of calibration. The millivolts of each sensor are actively
updated in real time on this screen.
There are two methods of high point calibration, the loop flush method and the
Head Only Calibration Kit (preferred).

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Revision NEW APECS™ 2.7 15 of 19
Date: 10 July 2008
APECS ™ OPERATIONAL
INSTRUCTIONS (v. 2.7)
Loop Flush High Point Calibration
1. Perform all Pre-dive check procedures up to the step “Complete
calibration if necessary”. To complete calibration, all performance checks
prior to this need to be completed. Insure that negative pressure check
step was good and apply another vacuum to the loop sucking all the
ambient air out of the loop. Next, close the vent valve on the exhaust
counterlung and fill the loop with 100% Oxygen until the vent valve vents
gas. Let set for 10 seconds.
2. Vacuum the loop again and fill again until the vent valve vents and repeat
above.
3. Open the vent valve all the way and tightly pinch the exhaust breathing
hose to isolate the exhaust counterlung from the oxygen bypass on the
inhalation counterlung.
4. Push the oxygen manual bypass for 3 seconds; this will blow 100%
oxygen over the sensors without increasing the loop pressure giving a
possible higher PO2 reading.
5. Repeat 4 above.
6. Repeat 4 again.
7. You now have a purged loop with nearly 100% Oxygen. You will observe
the sensor millivolt output in both displays and the normal output is in the
zone of 35 to 60 millivolts.
Note: The lower the sensor mv output at both points of calibration the
lower the sensor mv reading. Beware that the sensor is reaching its end of
useful life.
8. Push the yes button on the displays and you have finished the two point
calibration.

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Revision NEW APECS™ 2.7 16 of 19
Date: 10 July 2008
APECS ™ OPERATIONAL
INSTRUCTIONS (v. 2.7)
Head Only Calibration Kit
The optional Head Only Calibration Kit offers the distinct advantages of a more
accurate gas environment for the sensors, is quicker, and uses less oxygen than
the loop flush method.
1. Perform all Pre-dive check procedures up to the step “Complete
calibration if necessary”. To complete calibration, all performance checks
prior to this need to be completed. Your oxygen tank should be analyzed
at this point.
2. Disconnect the quick disconnect O2 fitting from the manual O2 add valve
on the inhale counterlung.
3. Insert the male plug from the kit to the center hose mount base on the
head (inhale hose mount). Insert hose with flow restrictor into male plug
and snap the other end of the hose (flow restrictor) into the LP Oxygen
hose fitting.
4. Connect female cap from the kit to the male fitting on the bottom of the
head. Insert hose about 3/4” into the female cap. Connect other end to
oxygen analyzer.
5. Turn on oxygen bottle and observe the mv display on the handset and the
PO2 reading on the analyzer.
6. Once the mv reading has stabilized at the highest reading obtainable and
the analyzer reading matches the value obtained when you analyzed the
O2 cylinder press the CONFIRM button and the highpoint calibration is
complete.
7. Repeat the steps above for the remaining handset.
Note: You may only calibrate one display at a time under the following
conditions; you have not changed the sensors or performed any electrical
work, and the millivoltage is within the 7.0 to 13.5 mv ambient air
specifications. Calibrating one display can help insure that you have one
display to monitor the PO2 during the purge procedure to help insure that
you are achieving the proper loop PO2 for calibration.
Warning! After calibration, both displays must be within 0.05 ATA/Bar of
each other.

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Revision NEW APECS™ 2.7 17 of 19
Date: 10 July 2008
APECS ™ OPERATIONAL
INSTRUCTIONS (v. 2.7)
DANGER! The
diver at all times must be aware of the proper operation of the primary and
secondary systems. If the primary display at anytime fails to activate and
display the PO2, your solenoid will not activate due to the failure. Both the
primary and the secondary display systems are programmed to go to sleep
for power conservation after 10 minutes of inactivity (i.e. no switch hits)
during the dive until reawaked. Depressing the CONFIRM or MENU switch
awakens the subsystem and this inactivity timeout will restart. While the
displays are asleep, normal oxygen injection, sensor voting logic and all
other essential processing continues in the background.
APECS / SHEARWATER PURSUIT CONFIGURATION
APECS 2.5A hardware, in combination with APECS 2.7 software, permits
safe integration of third party decompression solutions. At present only
one product has met the stringent criteria and testing for integration with
the Megalodon and that is the Shearwater Pursuit Dive Computer.
Integration is achieved by replacing the secondary APECS 2.5 board with
an Isolation board. The secondary battery box powers the isolation board
The Shearwater is powered by it’s own internal battery. The APECS
primary board provides information to the APECS handset and controls
both the HUD and the solenoid on APECS heads, and the HUD on COPIS 2
heads.
The Teledyne R22D cells are connected to the APECS 2.5 board and the
Isolation board. A fault with either the Isolation board or the Shearwater
system or cable will not affect the APECS unit and vice versa.
Operational instructions and operating procedures and limitations as well
as software updates and support are available directly from Shearwater
Research Inc. (www.rebreather.ca). InnerSpace Systems strongly
recommends the hardwired configuration for maximum reliability but can
supply the APECS 2.5A hardware configuration with a Fischer cable to
accommodate divers who wish to be able to disconnect the Pursuit from
the head.

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Revision NEW APECS™ 2.7 18 of 19
Date: 10 July 2008
APECS ™ OPERATIONAL
INSTRUCTIONS (v. 2.7)
APECS 2.5 A Hardware Configuration
Note: On COPIS2 configurations the solenoid will not be present.

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Revision NEW APECS™ 2.7 19 of 19
Date: 10 July 2008
APECS ™ OPERATIONAL
INSTRUCTIONS (v. 2.7)
REVISION INDEX
Date Revision CHANGES
10 JULY
2008
NEW