Aquacom MK-IV User manual

MK-IV
3-Diver Intercom
“Technology in Depth”
Full-Duplex Surface Station
for Underwater Communications
Aquacom®

i
- NOTICE -
This manual and the information contained herein are provided for use as a main-
tenance and operation guide. No license or rights to manufacture, produce, and/
or sell either the manual or articles described herein are given. Undersea Systems
International, Inc., dba Ocean Technology Systems hereinafter referred to as OTS,
reserves the right to change specications without notice. It is recommended that
all users read and fully understand this manual before using the MK-IV 3-Diver
Intercom.
All statements, technical information, and recommendations herein are based on
tests we believe to be reliable, but the accuracy or completeness thereof is not guar-
anteed; and the following is made in lieu of all warranties, expressed or implied,
including the implied warranties of merchantability and tness for purpose: Seller’s
and Manufacturer’s only obligation shall be to replace such quantity of the product
proved to be defective. Before using, the user shall determine the suitability of the
product for intended use, and the user assumes all risk and liability whatsoever in
connection therewith. Neither Seller nor Manufacturer shall be liable either in tort
or in contract for any loss or damage—direct, incidental, or consequential—arising
from the use of or the inability to use the product. No statement or recommenda-
tion not contained herein shall have any force or effect unless it is in an agreement
signed by ofcers of the Seller and Manufacturer.
- IMPORTANT SAFETY NOTICE -
(Please read before using product.)
It is absolutely essential that all operators are properly trained and equipped
and fully understand this user’s manual before attempting to use the MK-IV
3-Diver Intercom.
While the MK-IV provides good underwater communications, it does not
change or eliminate the potential hazards of diving!
506118-000 (J)
Copyright © 2010 by Undersea Systems International, Inc., dba
Ocean Technology Systems. All rights reserved.
Specications are subject to change without prior notice.
Refer to the Library page of our Web site, www.otscomm.com, for a list of
any changes made to this manual since its publication.
Undersea Systems International, Inc.
dba
Ocean Technology Systems

TABLE OF CONTENTS
Section 1: Introduction ...............................................................................1
1.1 General.........................................................................................1
1.2 Specications ...............................................................................2
Section 2: Equipment Description .............................................................3
2.1 Package Design............................................................................3
2.2 Included with the MK-IV.............................................................3
2.3 Additional Components, Sold Separately....................................3
2.3.1 Communication Cables ................................................. 3
2.3.1.1 ComRopes ...................................................3
2.3.1.2 Spiral Four ...................................................4
2.3.1.3 Shielded Cable.............................................5
2.3.2 Diver Microphones........................................................5
2.3.2.1 ME-16R Hot-Mic®(912086-000)................ 5
2.3.2.2 Super Mic®Depth Master............................ 5
2.3.2.3 Preamplied, Powered Microphones...........6
2.3.3 Earphone-Microphone (EM) Assemblies ......................6
2.3.3.1 EMA-2 (911060-001) ..................................6
2.3.3.2 EMA-2SM (911060-098) ............................6
2.3.3.3 EMX-2 (911060-008) ..................................6
2.3.3.4 EMX-2B (911060-026) ...............................6
2.3.3.5 EMO-2 (900096-686)..................................6
2.3.3.6 EMH2-1 (911060-009) ................................6
2.3.3.7 EMH2-1SM (911060-100) ..........................7
2.3.3.8 EMS-2 (911060-017)...................................7
2.3.3.9 LAR V Adapter (900282-000).....................7
2.3.3.10 EMD-2 (911060-067) ..................................7
2.3.3.11 EMD-2SM (911060-101) ............................7
2.3.3.12 EMDG-2 (911060-076) ...............................8
2.3.3.13 EMH1-1 (900332-000)................................8
2.3.3.14 EMH1-1SM (900332-001) ..........................8
2.3.3.15 EMMT-1 (911060-090) ...............................8
2.3.3.16 EMMT-1SM (911060-102)..........................8
2.3.3.17 EMMT-2 (911060-091) ...............................8
2.3.3.18 EMMT-2SM (911060-103)..........................8
2.3.4 HHM-IV Hand-Held Microphone .................................8
2.3.5 Umbilical Adapters........................................................8
2.4 Functions......................................................................................8
Section 3: Supplying Electrical Power .................................................... 11
3.1 Battery Power............................................................................. 11
ii

iii
3.1.1 Battery Charging.......................................................... 11
3.1.2 Battery Replacement ................................................... 12
3.2 AC Power...................................................................................13
3.2.1 Electrical Safety Mechanisms .....................................14
3.2.1.1 GFCI ..........................................................14
3.2.1.2 Thermal Breaker........................................15
3.3 External DC Power ....................................................................15
Section 4: Operation .................................................................................16
4.1 Adjustments and Controls..........................................................16
4.1.1 System Power ..............................................................16
4.1.2 Diver Controls .............................................................16
4.1.2.1 Diver Audio Volume Controls ...................16
4.1.2.2 INAC Control ............................................16
4.1.2.3 Microphone Type Selection.......................17
4.1.2.4 Diver PTT Control..................................... 18
4.1.3 Tender Control.............................................................18
4.1.4 Speaker Power and Volume.........................................19
4.2 Setup ..........................................................................................19
4.3 Reception ...................................................................................21
4.4 Transmission ..............................................................................22
4.5 Recording Communications.......................................................22
4.6 After the Dive ............................................................................22
4.7 Helpful Hints..............................................................................22
Section 5: Maintenance and Troubleshooting ........................................24
5.1 Preventive Maintenance.............................................................24
5.2 Troubleshooting .........................................................................24
Appendix: Spare Components and Parts ...............................................27
Limited Warranty .....................................................................................28
Tables
Table 1: Compatible EM Assemblies with Standard Microphones ........7
Table 2: Battery Voltage Indication ...................................................... 11
Table 3: Connectors and Wiring of External Devices...........................20
Table 4: Troubleshooting ................................................................25–26
Illustrations
Figure 1. Examples of Standard and Preamplied Microphones ...........4
Figure 2. MK-IV Panel Layout...............................................................9
Figure 3. Battery Panel Assembly ........................................................13
Figure 4. Electrical Safety Mechanisms ...............................................14
Figure 5. Location of Microphone Type Selection Switch...................17

SECTION 1
INTRODUCTION
Congratulations! You have just purchased one of the nest, state-of-the-art under-
water communication systems available. The Aquacom®MK-IV 3-Diver Intercom
allows open “round robin” communications through intercom lines among a surface
tender with a headset (included) and up to three divers with earphone-microphone
assemblies (sold separately). All users can speak and listen simultaneously, without
the need for a push-to-talk system that would interrupt communications.
The MK-IV 3-Diver Intercom represents the latest generation of intercom technol-
ogy with many useful features for outstanding performance, including an INAC
(Inhalation Noise Attenuation Circuit) for reduction of diver inhalation noise; a
MIL-spec speaker designed for high-quality sound; MIL-spec connectors for all
communication connections; capability of both powered (preamplied) and non-
powered microphones; remote speaker and record-out connections; GFCI and
transformer isolation for enhanced diver safety; a durable, heavy-duty housing;
and much more. In all, the MK-IV 3-Diver Intercom is second to none!
1.1 GENERAL
This manual contains much of the information you will need to know regarding the
Aquacom®MK-IV 3-Diver Intercom communication system. Section 1 contains a
table of specications and an overview of the functions of the MK-IV.
Before operating the MK-IV 3-Diver Intercom, read this entire manual. In addition
to the information presented on functions and operation, there are some important
safety issues all users must be familiar with before using the MK-IV. If you have
any questions, contact your local OTS dealer, or feel free to contact OTS directly
(see page 28 for OTS contact information).
1

2
1.2 SPECIFICATIONS
Input voltage: 90–264 V AC, 47–63 Hz
Input current: 5 amps DC
Idle current: 125 mA
Audio power: 16 watts max (4 watts per diver, 2 watts each
for tender headset and speaker)
Frequency response: 300–4000 Hz
Microphone input impedance: (Non-powered) 150 ohms
Headphone impedance output: 300 ohms
Protection circuits: GFCI: 10 mA through ground path
Thermal circuit breaker: 2 A slow trip
Battery type: Rechargeable, lead acid, 12 V, 5 Ah
Battery life: 14 hours continuous use (full charge)
Operating temperature: -40°C to 50°C (-40°F to 122°F)
(not charging batteries; not mains power)
-40°C to 40°C (-40°F to 104°F)
(w/ mains power and charging)
Note: Room temperature recommended for
charging.
Storage temperature: –25°C to 65°C (–13°F to 149°F)
Cabinet material: Molded composite
Front-panel material: 0.080” stainless steel, powder coated
Housing dimensions: Height: Lid on: 14-1/2 inches
Lid off: 8-1/2 inches
Width: 14 inches
Depth: 12-1/2 inches
Weight: 28 lbs.

SECTION 2
EQUIPMENT DESCRIPTION
2.1 PACKAGE DESIGN
The Aquacom®MK-IV 3-Diver Intercom is housed in a sturdy, impact- and rust-
resistant berglass case with stainless steel latches. The case is opened with a
counterclockwise rotation of the handles on the two buttery latches that secure
the lid; the lid can be fully opened and even removed easily at the hinge. The
conguration of the multiple sets of feet on the case allows the unit to stand safely
with the panel facing upward or forward.
The connectors and control knobs on the front panel are all military style and are
therefore constructed to a high quality standard, providing ruggedness and durabil-
ity for use in marine and other harsh environments.
The panel speaker meets military standard MIL-L-24296A and is built for durability
and endurance under demanding environmental conditions. Its resistance to shock,
vibration, and salt spray make it an excellent speaker for oceanic shipboard use.
2.2 INCLUDED WITH THE MK-IV
The following items are provided with the MK-IV:
• THB-16 tender headset with boom microphone (part no. 900298-032)
• AC power/charging cable (part no. 914081-000)
• Two (2) four-socket military-style (MS) connectors (OTS part no. 211106-000;
industry part no. MS3116F8-4S)
• MK-IV 3-Diver Intercom user’s manual (document no. 506118-000)
• Warranty card with the MK-IV unit’s serial number (doc. no. 506014-000)
2.3 ADDITIONAL COMPONENTS, SOLD SEPARATELY
2.3.1 COMMUNICATION CABLES: Each diver requires an intercom cable
for connection from his earphone and microphone to the MK-IV. Be sure to obtain
the 5-pin military-style plug on one end that matches the diver umbilical receptacles
(Section 2.4, Item 5) on the MK-IV (refer to Table 3, Item 1 in Section 4.2). The
other end of the cable should have the connector for your particular earphone-
microphone assembly.
2.3.1.1 ComRopes: OTS offers ComRopes consisting of communication cables
bundled inside a durable yet exible rope. Various lengths of ComRopes are avail-
able with connectors to match different earphone-microphone assemblies. Contact
OTS or your local OTS dealer for information about available ComRopes for use
with the MK-IV.
3

2.3.1.2 Spiral Four: This cable has been used extensively with military and
commercial divers for many years. It has been available as military surplus but is
becoming harder to nd. However, there are some cable manufacturers that have
duplicated this cable, and it is now available to the diving community.
The most important feature of this cable is the internal wires used for microphone
and earphone circuits. Usually, there are two white and two brown or black cables,
congured in a twisted pattern. Always connect the speaker or microphone to either
the white pair or the black (brown) pair. If this is not done, electrical feedback
(squeal) will occur. When connected correctly, the cable is balanced, and clear
communication is possible.
4
Figure 1. Examples of Standard and Preamplied Microphones
(A) Non-powered, dynamic mic (ME-
16R Hot-Mic® for Interspiro
FFM)
(B) Non-powered, dynamic mic
(Shure microphone for band
mask or SuperLite®helmet)
(D) Powered (preamplied) micro-
phone for band mask or Super-
Lite®helmet)
(C) Powered (preamplied) micro-
phone for Interspiro FFM

2.3.1.3 Shielded Cable: Another available cable contains at least one twisted,
shielded balanced cable and a second twisted, shielded or unshielded pair. The
unshielded pair is used for the earphones, while the balanced, twisted pair is used
for the microphone. Unlike spiral four cable, little can go wrong with this system,
provided the microphone is connected to the shielded, twisted, balanced cable.
2.3.2 DIVER MICROPHONES
See Figure 1 for examples of non-powered and powered (preamplied) micro-
phones.
2.3.2.1 ME-16R Hot-Mic
®
(912086-000): The ME-16R Hot-Mic
®
(Fig. 1A) is
a 150-ohm, water-resistant microphone element. It is a state-of-the art dynamic
microphone element designed to give you long, trouble-free use and the highest
intelligibility possible.
Although the Hot-Mic is trouble free, it should be maintained. Rinse it with
freshwater after use to get all dirt, debris, or salt water from the grill. Dry it with a
clean, soft towel. If the element ever needs to be replaced, it is easily removed by
unscrewing the two small screws located on its base.
Getting the microphone wet does not harm it. However, the microphone element
can only withstand an 8- to 10-foot depth/pressure differential. If you removed your
diving FFM at the back of the boat and the microphone became wet, there would
be no problem; but if the FFM with element dropped more than 8 to 10 feet into the
water, the change in pressure probably would damage the microphone element. In
tests we have taken off the FFM at 30 feet and replaced it, still at 30 feet, without
any problem; but if one were to take off the FFM at 30 feet and drop down to 40
feet, the pressure difference may damage the microphone.
2.3.2.2 Super Mic
®
Depth Master: The Super Mic
®
offers patented technol-
ogy* that overcomes a limitation of other microphones. It can be used at any depth
and—unlike the Hot-Mic or many other microphones—can withstand changes in
depth while submerged, so it will not be damaged if the diver needs to descend
with the mask ooded (such as when a full-face mask is removed and stowed
when the diver changes to another air system). It is a ceramic microphone with a
compact, lightweight design and noise-cancelling properties, reducing background
noises for clearer communications. When only the highest quality of intelligibility
is required, the Hot-Mic is the preferred choice; but the Super Mic’s intelligibility
is sufcient for most diving situations.
To assure clear communications when using the Super Mic, it should be no more
than 1/4 inch from the corner of the diver’s mouth.
After each dive, clean the Super Mic by rinsing it with freshwater and drying it
with a clean, soft towel. No other maintenance is required.
5
*U.S. Patent no. 7,170,822; EU patent nos. 000458351-0001, -0002, -0003, -0004, -0005, -0006.

Note: Do not press on the microphone diaphragm; doing so may cause damage.
2.3.2.3 Powered, Preamplied Microphones: The MK-IV supports the use
of preamplied microphones (Fig. 1C & D), which tend to be more durable and
rugged and require less maintenance than standard microphones—although they
often have lower delity, with somewhat diminished dynamic range and speech
intelligibility. Powered microphones are available separately with two-contact
connectors or can be custom-tted with earphones, depending on your particular
requirements. For information on available powered microphones, contact OTS
or your local OTS dealer.
2.3.3 EARPHONE-MICROPHONE (EM) ASSEMBLIES: We offer our
standard microphones integrated into earphone-microphone (EM) assemblies
designed to t the communication port of full-face masks (FFMs) produced by
various manufacturers. Table 1 is a compatibility chart of some of the standard
(non-powered) EM assemblies available for use with a ComRope connected to the
MK-IV 3-Diver Intercom. Note: If you have a diving helmet or mask that is not on
the compatibility chart, contact OTS or your local OTS dealer for availability or
for information on custom EM assemblies.
The following are full descriptions of each of the EM assemblies listed in Table
1:
2.3.3.1 EMA-2 (911060-001): The EMA-2 EM assembly is designed for all
Divator MKII (“AGA”) full-face masks (FFMs). It has two ceramic earphones with
holders, an ME-16R Hot-Mic, a Hi-Use®connector, and a push-to-talk (PTT) but-
ton. The assembly is installed into the Divator MKII FFM communication port.
2.3.3.2 EMA-2SM (911060-098): The EMA-2SM EM assembly is designed
to be installed into all Divator MKII (“AGA”) FFMs. It consists of two ceramic
earphones with holders, a Super Mic, a Hi-Use®connector, and a PTT button. The
assembly is installed into the Divator MKII FFM communication port.
2.3.3.3 EMX-2 (911060-008): The EMX-2 EM assembly is designed for the
EXO-26 original FFM. It consists of two dynamic earphones, an ME-16R Hot-
Mic, a Hi-Use®connector, and a PTT button.
2.3.3.4 EMX-2B (911060-026): The EMX-2B EM assembly is designed for the
EXO-26 standard full-face mask. It is similar to the EMX-2 but ts the balanced-
regulator version of the EXO-26 with an oral-nasal cavity.
2.3.3.5 EMO-2 (900096-686): The EMO-2 EM assembly is designed to be in-
stalled into the Ocean Reef NIRA Neptune FFM. It has two earphones with holders,
a Hot-Mic, a Hi-Use®connector, and a PTT button. It is installed into a port on the
side of the FFM.
2.3.3.6 EMH2-1 (911060-009): The EMH-1 EM assembly is optionally included
with the HM-2 mouth mask. It has one head strap, one ceramic earphone, a Hot-
6

Mic, a Hi-Use®connector, and a PTT button (located on the HM-2 mask).
2.3.3.7 EMH2-1SM (911060-100): The EMH-1SM EM assembly is optionally
included with the HM-2 mouth mask. It has a head strap, one ceramic earphone, a
Super Mic, a Hi-Use®connector, and a PTT button (located on the HM-2 mask).
2.3.3.8 EMS-2 (911060-017): The EMS-2 is an EM assembly designed to be
installed into a ScubaPro FFM. It consists of two earphones with holders, a Hot-
Mic, a PTT button, and a Hi-Use®connector.
2.3.3.9 LAR V Adapter (900282-000): This adapter is placed between the in-
halation hose and LAR V bite-mouth/DSV T-bit assembly. It is designed to allow
basic words to be transmitted without the need for a full or half mask. It consists of
one earphone, an ME-500 microphone, a Hi-Use®connector, and a PTT button.
7
Table 1: Compatible EM Assemblies with Standard Microphones
Model Number
Part Num-
ber
Micro-
phone
Earphones
Mask Type
Sin-
gle Dual
EMA-2 911060-001 Hot-Mic
®
X All Divator MK II FFMs
EMA-2SM 911060-098 Super
Mic
®
X All Divator MK II FFMs
EMX-2 911060-008 Hot-Mic
®
X EXO-26 original FFM
EMX-2B 911060-026 Hot-Mic
®
X EXO-26 standard FFM
EMO-2 900096-686 Hot-Mic
®
X Ocean Reef FFM
EMH2-1 911060-009 Hot-Mic
®
X HM-2 mouth mask
EMH2-1SM 911060-100 Super
Mic
®
X HM-2 mouth mask
EMS-2 911060-017 Hot-Mic
®
X ScubaPro FFM
LAR V
Adapter 900282-000 Dynamic mic XLAR V mouthpiece
EMD-2 911060-067 Hot-Mic
®
X M-48 SuperMask
®
FFM
EMD-2SM 911060-101 Super
Mic
®
X M-48 SuperMask
®
FFM
EMDG-2 911060-076 ME-500 X Dräger Panorama Nova Dive
Mask
EMH1-1 900332-000 Hot-Mic
®
X HM-1 mouth mask
EMH1-1SM 900332-001 Super
Mic
®
X HM-1 mouth mask
EMMT-1 911060-090 Hot-Mic
®
X Mantis FFM
EMMT-1SM 911060-102 Super
Mic
®
X Mantis FFM
EMMT-2 911060-091 Hot-Mic
®
X Mantis FFM
EMMT-2SM 911060-103 Super
Mic
®
X Mantis FFM

8
2.3.3.10 EMD-2 (911060-067): The EMD-2 EM assembly is designed to be
installed into the M-48 SuperMask® FFM. It consists of two earphones, earphone
holders, a Hot-Mic, a Hi-Use®connector, and a PTT button.
2.3.3.11 EMD-2SM (911060-101): The EMD-2SM EM assembly is designed to
be installed into the M-48 SuperMask® FFM. It consists of two earphones, earphone
holders, a Super Mic, a Hi-Use®connector, and a PTT button.
2.3.3.12 EMDG-2 (911060-076): The EMDG-2 EM assembly is designed to be
installed into the Dräger Panorama Nova Dive Mask. It consists of two earphones,
earphone holders, an ME-500 microphone, a Hi-Use®connector, and a PTT but-
ton.
2.3.3.13 EMH1-1 (900332-000): The EMH-MAG2 EM assembly is designed to
be installed into the HM-1 silicone half mask. It consists of one earphone, a Hot-
Mic, a Hi-Use®connector, and a PTT button.
2.3.3.14 EMH1-1SM (900332-001): The EMH-MAG2SM EM assembly is de-
signed to be installed into the HM-1 silicone half mask. It consists of one earphone,
a Super Mic, a Hi-Use®connector, and a PTT button.
2.3.3.15 EMMT-1 (911060-090): The EMMT-1 EM assembly is designed to be
installed into the Mantis FFM. It consists of one earphone, an earphone holder, a
Hot-Mic, a Hi-Use®connector, and a PTT button.
2.3.3.16 EMMT-1SM (911060-102): The EMMT-1SM EM assembly is designed
to be installed into the Mantis FFM. It consists of one earphone, an earphone holder,
a Super Mic, a Hi-Use®connector, and a PTT button.
2.3.3.17 EMMT-2 (911060-091): The EMMT-2 EM assembly is designed to be
installed into the Mantis FFM. It consists of two earphones, two earphone holders,
a Hot-Mic, a Hi-Use®connector, and a PTT button.
2.3.3.18 EMMT-2SM (911060-103): The EMMT-2SM EM assembly is designed
to be installed into the Mantis FFM. It consists of two earphones, two earphone
holders, a Super Mic, a Hi-Use®connector, and a PTT button.
2.3.4 HHM-MKIV HAND-HELD MICROPHONE: As an alternative to
the THB-16 headset, a hand-held microphone (the HHM-MKIV) is available. It
should be used if the tender prefers to use the panel speaker instead of the head-
set’s earphone to listen to received communications. Unlike use of the THB-16
headset, the PTT button on the HHM-MKIV must be pressed in order to transmit.
This feature is useful if the tender does not want to transmit constantly.
2.3.5 UMBILICAL ADAPTERS: OTS offers adapters to interface to your
current umbilical/communications cables. OTS offers a 6-pin to 5-pin (p/n 914085-
000) military style adapter for use with Hydrocomm cables. Another available
adapter is a double banana to 5-pin (p/n 914085-001) military connector for use
with communication cables having standard double banana plug connectors.

Figure 2. MK-IV Panel Layout
9
2.4 FUNCTIONS
Figure 2 depicts the MK-IV panel with its controls and connections. The numbered
text below is the key to the indexed items in Figure 2. Boldfaced text in all capital
letters refers to the label on the panel.
1. DIVER MOUTH VOLUME (1 of 3): Volume control knob for listening
to diver speech. Separate volume controls are provided for the three diver
connections. Rotate the knob clockwise to increase and counterclockwise to
decrease the volume.
2. INAC indicator (1 of 3): This red LED indicator illuminates to indicate when
the INAC function is active, reducing noise levels. One indicator is provided
for each diver.
3. INAC LEVEL (1 of 3): This knob controls the INAC sensitivity. A separate
INAC control is provided for each diver. A clockwise rotation increases the
sensitivity to shut off the diver transmission more readily in response to diver
inhalation noise. A full counterclockwise turn past the detent shuts off the
INAC.
4. DIVER EAR VOLUME (1 of 3): A knob is provided for adjustment of the
receive volume for each diver earphone. Clockwise rotation increases and

10
counterclockwise rotation decreases the volume.
5. UMBILICAL (1 of 3): The ve-socket military-style (MS) receptacles for
connecting the cables from the diver earphone-microphone assemblies.
6. TENDER MOUTH VOLUME: This knob controls the output audio volume
from the microphone on the tender headset (or optional HHM-MKIV hand-
held microphone, sold separately). The setting affects the audio heard by all
divers.
7. HEADSET: This six-contact, military-style (MS) receptacle accepts the con-
nector from the supplied THB-16 tender headset or the optional HHM-MKIV
hand-held microphone, sold separately.
8. MIC POWER: This LED illuminates red to indicate when the microphone
type selection switch (see Section 4.1.2.3 and Fig. 4) is set to the “power mic”
position, so that power is supplied to the microphone.
9. CHARGE indicator: When AC power is supplied (Item 9), this LED indica-
tor illuminates red or green to indicate the charging status of the battery (see
Section 3.1.1).
10. AC/CHARGER power: A four-pin military-style (MS) connector for provid-
ing external AC power to charge the battery (Section 3.1.1) or to operate the
unit using AC power (Section 3.2).
11. POWER switch: A two-position toggle switch for turning on and off the
MK-IV power.
12. 12 VOLT DC POWER: A receptacle that accepts a double banana plug from
a 12-volt DC power source, as an alternate to the internal battery or an AC
power source.
13. BATTERY LEVEL: Three LEDs that illuminate to indicate the battery volt-
age level, as explained in Section 3.1.
14. Handle (1 of 2): Handles for lifting either the MK-IV unit (with the case open)
or the panel out of the case.
15. RECORD OUT: A four-pin military-style (MS) plug for connecting a record-
ing device (see Section 4.2, Step 5). The mating connector is provided with
the MK-IV.
16. AUX SPEAKER: A four-pin military-style (MS) plug for connecting an
external auxiliary speaker (see Section 4.2, Step 5). The mating connector is
provided with the MK-IV.
17. HSU: A six-contact military-style (MS) receptacle for connecting a helium-
speech unscrambler (HSU).
18. SPEAKER VOLUME: Control knob for adjusting the audio volume of the
front-panel speaker (and an external speaker, if connected). A full counter-
clockwise rotation past the detent turns off the speaker.
19. Panel speaker: The front-panel speaker for listening to the divers’ commu-
nications without a headset.
20. Speaker switch: A switch for turning on and off the panel speaker (#19).
21. Panel screw (1 of 14): These fourteen #10-32 Phillips screws secure the panel
to the case. They should be maintained at moderate tightness.

SECTION 3
SUPPLYING ELECTRICAL POWER
The MK-IV 3-Diver Intercom provides three options for power supply: the internal
RB-1 battery, 90–240 volts AC power (at 50/60 Hz), or an external 12-volt DC
power supply. The best option for you will depend on your particular application
(see Section 4.2 for information on setup of the MK-IV).
3.1 BATTERY POWER
Inside the MK-IV is an RB-1 six-cell lead-acid battery, which supplies 12 volts at
5.0 amp-hours. The RB-1 is the latest in state-of-the-art battery technology, pro-
viding a long service life, high cycle life, superior reliability even under extreme
conditions and use, and relative safety (minimal or no gassing under normal charg-
ing conditions). The RB-1 is recognized by Underwriters Laboratories (UL) as a
component and meets UL1989.
Use the battery level indicator LEDs (Fig. 2, #13) to monitor the voltage level of the
internal battery. The battery’s charge status is indicated by the LEDs and beep tone
sounds as described in Table 2. When the battery charge drops to approximately 6
volts, the MK-IV’s power will shut off. Refer to Section 3.1.1 for information on
recharging the battery.
3.1.1 BATTERY CHARGING: The MK-IV is equipped with an internal bat-
tery charger, so one only has to connect the MK-IV to an AC power source (per
the instructions in Section 3.2) to recharge the battery.
Safety Precautions:
1. While charging the battery it is very important to open the MK-IV’s lower
safety vent (located on the front of the case’s lower half when the panel faces
upward) by unscrewing the ventilation valve fully counterclockwise. Ideally,
while the batteries recharge, the MK-IV should be rotated 90 degrees onto
the back of the case such that the valve is facing up; in the event of a charger
Table 2: Battery Voltage Indication
LED Color LED Status Beep Tone Voltage1
Green Solid None Above 9 V
Yellow Solid None 9 V
Red Solid Every 30 sec. 8 V
Red Blinking Every 30 sec. 7 V
Red Blinking Every 15 sec. 6.5 V
1. These values are approximate and should be used only as an estimate.
11

failure or defective battery cell, gasses released during charging can thus dis-
sipate out of the unit through the vent (the released gasses are lighter than air
and travel upward). Allow at least 20 minutes after charging for any gasses
to dissipate before returning the unit to its operating position and closing the
ventilation valve (by rotation fully clockwise, to prevent water entry).
2. Because the ventilation port should be open while AC power is used and the
battery recharges, the MK-IV should be operated in such a way as to minimize
contact with splashing or spraying water. Operation away from direct contact
with salt water or freshwater splashes or sprays is always recommended when
operating 110/220-volt mains-powered electronics.
A fully depleted battery can be recharged completely in about 3–5 hours.
While the battery is being charged and its voltage is below maximum, the charge
indicator LED (Fig. 2, #9) illuminates red in color. When the battery has been com-
pletely recharged, the charger will enter trickle-charge mode to maintain maximal
battery voltage, indicated by green illumination of the charge indicator LED.
3.1.2 BATTERY REPLACEMENT: The RB-1 battery should provide a long
lifetime of service through many depletion and recharging cycles. Nevertheless,
eventually the battery may cease maintaining an adequate charge; in this event you
will have to replace the battery. Replacement RB-1 batteries (part no. 910319-000)
are available from OTS or your local OTS dealer.
Follow these instructions to replace the RB-1 battery:
1. Ensure the power switch (Fig. 2, #11) is toggled to the off position. If the unit
is connected to an external power source, unplug the power cable from it.
2. Disconnect all devices attached to the front panel.
3. Using a #2 Phillips screwdriver, remove and set aside the fourteen panel screws
(Fig. 2, #21) and neoprene seals.
4. Using the two handles (Fig. 2, #14), remove the front panel. The MK-IV’s
internal hardware and electronics are attached to the panel, so it is fairly heavy
and requires special care when being handled.
5. Disconnect the battery leads (on opposite ends of the battery) (Fig. 3, #3) using
a slotted screwdriver. IMPORTANT NOTE: Always disconnect the negative
(black) lead rst to prevent accidental short-circuiting.
6. Remove and set aside the four screws (Fig. 3, #1) and lock nuts (#5) that secure
the battery (#2) to the battery tabs (#4).
7. Lift or slide out the battery from the tabs.
8. Replace the battery with the new one, installing it with the terminals down and
with the top of the battery (with the label) facing away from the electronics on
the battery plate. The + and – signs should be oriented as illustrated in Figure
3.
9. Replace the four screws and lock nuts. Tighten them securely without over-
12

tightening.
10. Connect the battery leads (red = positive, black = negative) as marked on the
battery. IMPORTANT NOTE: Always connect the positive (red) lead rst.
11. Reinstall the MK-IV panel, being careful not to contact the thermal breaker
(Fig. 3, #7) and GFCI (#6) switches against the ange of the case (doing so
might trip the switches). (Note: The proper setting for both switches is to
“ON,” indicated on the GFCI switch as the 1 showing instead of the 0 and
the adjacent indicator C10 colored red instead of green.)
12. Secure with moderate tightness the panel to the case with the fourteen screws
and seals.
13. Reconnect all devices to the front panel.
3.2 AC POWER
To operate the MK-IV using AC power, connect the supplied AC power/charging
cable to the panel connector (Fig. 2, #10). Connect the cable’s power plug to an
AC power outlet that supplies 90–240 volts at 50/60 Hz. Operation of the unit
with AC power will supply charging current to the battery. See Section 3.1.1 for
safety precautions.
Note: The standard AC power cable has a plug compatible with the standard electri-
cal outlets used in the U.S.A. However, if you need a plug for a different region of
the world, appropriate power cords are available from OTS or your OTS dealer.
3.2.1 ELECTRICAL SAFETY MECHANISMS: The MK-IV provides two
13
Figure 3. Battery Panel Assembly
Key
1. Retainer
screws (4)
2. Battery
3. Battery leads (2)
4. Battery bracket
5. Retainer nuts (4)
6. GFCI
7. Thermal breaker

mechanisms for electrical safety when AC power is used: a GFCI and a thermal
breaker. These allow for the remote possibility of an electrical failure that could
otherwise present a risk of electrical shock. Such an event is extremely unlikely,
but if it were to occur, the safety mechanisms would immediately deactivate the
unit’s power as a precaution to prevent personal injury or damage to the MK-IV.
3.2.1.1 GFCI: The GFCI (ground fault circuit interrupter) protects the divers by
immediately cutting off power to the unit in the unlikely event of a system failure,
such as failure of the power supply (Fig. 4, #6), that could otherwise send excess AC
current down the communications lines to the divers. The GFCI trips to deactivate
the power when the AC current is diverted to a ground.
The GFCI can be accessed for troubleshooting or testing. To do so, it is necessary
to remove the panel assembly (follow steps 1–4 of Section 3.1.2). IMPORTANT
NOTE: Because of the possibility of electrical shock when the panel is opened,
the GFCI should be accessed only by a qualied technician; furthermore, the
MK-IV must be in a dry environment and on a stable surface. Refer to Figure 3,
Item 6, for the location of the GFCI. A green LED (Fig. 4, #2) dimly illuminates to
indicate the GFCI is active. A status window (Fig. 4, #3) shows a red color if the
GFCI is active or green if it has been tripped to deactivate AC power.
When the GFCI trips, the unit’s power is immediately deactivated, as indicated by
the charging indicator LED’s (Fig. 2, #9) turning off. Also, the GFCI switch (Fig.
4, #4) moves to the “off” position, the power indicator LED (Fig. 4, #2) turns off
(although this can be difcult to determine because its illumination is very dim),
and the GFCI status window shows a green color. The unit’s power cannot be
reactivated from an AC source until the GFCI is reset, although power can still be
obtained from batteries or an external DC source.
Figure 4. Electrical Safety Mechanisms
14
Key
1. GFCI test button 4. GFCI toggle switch
2. GFCI power indicator 5. Thermal breaker toggle switch
3. GFCI status indicator 6. Charger/power supply

If AC power will be used, It is a good idea to test the GFCI before each use of the
MK-IV, to verify that the fail-safe mechanism works for assurance of diver safety.
As explained previously, this test must be done away from water, to prevent risk of
electric shock with the unit’s panel opened; and it should be done only by a quali-
ed technician. To test the GFCI, press the “test” button (Fig. 4, Item 1) on the
GFCI case. The power should immediately deactivate. (If it does not, contact OTS
for assistance. Do not use the MK-IV until this problem is solved.) IMPORTANT:
Be sure to move the GFCI switch back to the “on” position, or the unit’s power
will not activate.
3.2.1.2 Thermal Breaker: The thermal circuit breaker (Fig. 3, #7) monitors the
amount of AC current passing through the circuit. If the internal power supply (Fig.
4, #6) were to fail, allowing excessive current to pass through, then the thermal
breaker would trip, deactivating AC power to the unit.
If the thermal breaker trips, it must be reset before the MK-IV can be used again
with AC power. To do so, the panel assembly must be removed (follow steps 1–4
of Section 3.1.2). IMPORTANT NOTE: Because of the possibility of electrical
shock when the panel is opened, the thermal breaker should be accessed only by
a qualied technician; furthermore, the MK-IV must be in a dry environment
and on a stable surface. Refer to Figure 3, Item 7, for the location of the thermal
breaker.
When the thermal breaker trips, the unit’s power is immediately deactivated, as
indicated by the charging indicator LED’s (Fig. 2, #9) turning off. The unit’s power
cannot be reactivated from an AC source until the thermal breaker is reset, although
power can still be obtained from batteries or an external DC source.
3.3 EXTERNAL DC POWER
To operate the MK-IV using an external 12-volt DC power source (such as a lead-
acid battery of 5.0 Ah or other DC power supply), connect electrical cables via
a standard double banana plug to the DC power receptacle (Fig. 2, #10) on the
MK-IV front panel. Be sure to connect the negative lead to the black socket and
the positive to the red.
If the voltage of the external DC power source falls below that of the internal bat-
tery, the MK-IV will begin to draw current from both power sources. Therefore,
the battery level indicator (Fig. 2, #13) will monitor the voltage of both the internal
battery and the external DC source.
15

SECTION 4
OPERATION
The Aquacom® MK-IV 3-Diver Intercom, while providing a variety of powerful
functions and features, is relatively simple to set up and operate by following the
instructions provided here.
4.1 ADJUSTMENTS AND CONTROLS
The MK-IV 3-Diver Intercom has various controls that allow you to customize
and adjust the settings to your preference, to provide optimal communications for
your situation. This section describes the available controls.
4.1.1 SYSTEM POWER: Once a power source is available (Section 3), the
power switch on the front panel (Fig. 2, #11) toggles the unit’s power on and off.
4.1.2 DIVER CONTROLS:
4.1.2.1 Diver Audio Volume Controls: The microphone and earphone audio
signal volume levels are separately adjustable for each diver (Fig. 2, #1 and #4),
so you can adjust the levels to provide the best combination for all divers and the
tender to hear the communications comfortably.
4.1.2.2 INAC Control: The U.S. Navy rst put the Inhalation Noise Attenuation
Circuit (INAC) into use more than 20 years ago. The purpose of this circuit was to
reduce inhalation noise produced by preamplied microphones that tend to boost
high-frequency noise. This noise is loudest in some (but not all) diving masks and
helmets.
Depending on the microphone-mask combination, the INAC does attenuate diver
inhalation noise. However, if the microphone, mask, and regulator produce low
noise levels, the INAC does not operate correctly, because the INAC relies on noise
levels that are much higher than that of divers’ speech. A diver’s speech will be cut
off if inhalation noise levels are insufcient for the INAC to function correctly.
We therefore advise you to use the INAC only when warranted by inhalation noise
levels; otherwise, the INAC controls should be set to the “off” position.
The INAC level control (Fig. 2, #3) allows you to turn on and off the INAC circuit
and to adjust the INAC detection sensitivity for each diver. A higher sensitivity
setting causes the INAC to turn off the diver’s microphone more readily when in-
halation is detected. Adjust the sensitivity for each diver such that speech is heard
but inhalation breathing noise is not.
A red LED (Fig. 2, #2) is provided for each diver’s INAC control; it illuminates
to indicate that the INAC is active, reducing noise.
4.1.2.3 Microphone Type Selection: The MK-IV accommodates both powered,
16