Amron 2820A-02 User manual

User Manual
For
Amron International, Inc.
Models 2820A-02 & 2820A-03
Chamber Communicators
S/N ____________________
1380 Aspen Way, Vista California 92081-8349
United States of America
Phone: [phone]
Fax [phone]
Email: [e-mail]
Web: www.amronintl.com
This manual and the information contained herein are provided for use as an operation and maintenance
guide. No license or rights to manufacture, reproduce, or sell either the manual or articles described
herein are given. Amron International, Inc. reserves the right to change specifications without notice.
Copyright© 2018 Amron International, Inc.

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TABLE OF CONTENTS
1INTRODUCTION...................................................................................................................................1
2SPECIFICATIONS................................................................................................................................2
2.1 ELECTRICAL................................................................................................................................2
2.2 MECHANICAL...............................................................................................................................2
3ACCESSORIES....................................................................................................................................3
3.1 AMRON HEAVY-DUTY HEADSET - MODEL 2401-28................................................................3
3.2 AMRON STANDARD HEADSET - MODEL 2460-28....................................................................3
3.3 AMRON SINGLE EARPIECE HEADSET – MODEL 2460SM-28.................................................3
3.4 AMRON CHAMBER HEADSET - MODEL 2460-31R...................................................................3
3.5 AMRON CHAMBER EXTENSION CABLE – MODEL 2460-31R-25............................................3
3.6 AMRON REMOTE WALK-AND-TALK MODULE - MODEL 2822-28...........................................3
3.7 AMRON REMOTE PUSH-TO-TALK MODULE - MODEL 2821-28..............................................3
3.8 AUDIO ADAPTOR CABLE - AMRON PART NUMBER 180-1000-00..........................................4
3.9 AMRON CHAMBER COMMUNICATION BOX – MODEL 3113...................................................4
3.10 AMRON CHAMBER COMMUNICATION BOX – MODEL 3113...................................................4
3.11 AMRON CHAMBER COMMUNICATION BOX – MODEL 3115...................................................4
3.12 AMRON CHAMBER COMBO BOX – MODEL 3125.....................................................................4
3.13 AMRON CHAMBER COMBO BOX – MODEL 3126.....................................................................4
3.14 AMRON CHAMBER JUNCTION BOX – MODEL 3127................................................................4
3.15 AMRON CHAMBER WIRING HARNESS – MODEL 3128...........................................................5
3.16 AMRON CHAMBER ENTERTAINMENT SPEAKER – MODEL 3130..........................................5
4CONTROLS AND CONNECTIONS......................................................................................................6
4.1 OPERATOR AND LOCK CONTROLS .........................................................................................6
4.2 OPERATOR CONNECTIONS ......................................................................................................8
4.3 BACK PANEL CONNECTIONS....................................................................................................9
4.4 DRAWING, OPERATOR HEADSET CONNECTIONS...............................................................11
4.5 DRAWING, PUSH-TO-TALK CONNECTIONS...........................................................................12
4.6 DRAWING, 2820A-02 & 2820A-03 TO CHAMBER WIRING DIAGRAM....................................13
5OPERATION.......................................................................................................................................14
5.1 CHARGING THE BATTERY.......................................................................................................14
5.2 INITIAL POWER ON - BATTERY CONDITION CHECK............................................................14
5.3 OPERATING ON AC POWER....................................................................................................15
5.4 MODES OF OPERATION...........................................................................................................15
5.5 SETTING THE VOLUME CONTROLS.......................................................................................15
6MAINTENANCE..................................................................................................................................17
6.1 CHAMBER COMMUNICATOR CHECK PROCEDURES...........................................................17
6.2 GENERAL MAINTENANCE........................................................................................................18
6.3 RECOMMENDED MAINTENANCE SCHEDULE.......................................................................18

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7TROUBLESHOOTING........................................................................................................................20
7.1 CONNECTION ISSUES..............................................................................................................20
7.2 LOW BATTERY INDICATION.....................................................................................................20
7.3 UNIT NOT OPERATING.............................................................................................................20
7.4 LOW VOLUME............................................................................................................................21
7.5 GARBLED VOICE TO CHAMBER..............................................................................................21
7.6 GARBLED VOICE TO OPERATOR ...........................................................................................21
7.7 CHAMBER CUTS OFF...............................................................................................................21
7.8 FEEDBACK FULL DUPLEX (4-WIRE) MODE............................................................................21
7.9 PUSH-TO-TALK DOES NOT WORK..........................................................................................22
8DRAWINGS ........................................................................................................................................22
8.1 FRONT PANEL PARTS LOCATOR, MODEL 2820A-02............................................................23
8.2 FRONT PANEL PARTS LOCATOR, MODEL 2820A-03............................................................24
8.3 REAR PANEL PARTS LOCATOR, MODELS 2820A-02 & 2820A-03........................................25
8.4 MOUNTING DETAIL, MODELS 2820A-02 & 2820A-03.............................................................26
9PARTS LISTS.....................................................................................................................................27
9.1 MODELS 2820A-02 & 2820A-03 ................................................................................................27
9.2 2820A-02 & 2820A-03 FRONT PANEL COMPONENTS ...........................................................27
9.3 2820A-02 & 2820A-03 REAR CHASSIS COMPONENTS..........................................................28
9.4 2820A-02-03-FS FIELD SPARES KIT, 2820A-02 & 2820A-03..................................................28
9.5 2820A-02 & 2820A-03 OPTIONAL SPARES..............................................................................28
10. WARRANTY AND SERVICE POLICY...............................................................................................29
LIMITED WARRANTY..................................................................................................................2910.1 SERVICE POLICY........................................................................................................................2910.2

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1 INTRODUCTION
The Amron International AMCOM II 2820A-02 and 2820A-03 are full featured; two lock chamber
communication systems that provide reliable, two-way communications between the chamber
operator and occupants. Both models are used in conjunction with chamber talk back speakers such
as the Amron Model 3113, 3114, 3115, 3125 or 3126. The AMCOM II chamber communicators
include a rechargeable battery that maintains communication in the event of a power failure along
with a universal input 90-264 VAC, 47-440 Hz internal power supply. The 2820A-03 has all the
features of the 2820A-02 but also includes a separate entertainment amplifier circuit. This circuit is
used with the Amron Model 3130 Entertainment Speaker to provide audio entertainment to the
chamber occupants.
The AMCOM II Chamber Communicators have independent volume controls for the operator, inner
lock and output lock. There are separate on-off controls for each lock and both models are supplied
with the Amron Model 2405-28 Push-to-Talk microphone for use by the operator. The 2820A-02 and
2820A-03 can operate in 2-Wire or Full Duplex (4-Wire) modes as described later in this manual.

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2 SPECIFICATIONS
2.1 ELECTRICAL
Input Impedance (Each Input) ................................................................................... 250 Ohms
Frequency Response ........................................................................................ 300 - 10000 Hz
Common Mode Rejection ..................................................................................40 dB Minimum
Current Drain Maximum Full Volume .............................................................................3 Amps
Minimum Quiescent ................................................................................................ 0.190 Amps
Output Impedance ........................................................................................................... 4 Ohm
Power Supply Voltage ........................................ 12 VDC Nominal (9 VDC Min - 16 VDC Max)
AC Power Operating Range .................................................................90-264 VAC, 47-440 Hz
Sensitivity (Input) .............................................................................................................0.5 mV
Output Power (RMS @ 4 Ohm Load, 12 VDC) ..................................................10 Watts Audio
Battery Life ................................................................................................................... 45 Hours
2.2 MECHANICAL
Panel ............................................................................................................... Stainless Steel
Enclosure ......................................................................................... Black Anodized Aluminum
Width ...........................................................................................................10.1 in. (25.7 cm)
Depth .............................................................................................................7.5 in. (19.1 cm)
Height .............................................................................................................8.0 in. (20.3 cm)
Weight with Battery.............................................................................................14 Lbs. (6.4 kg)

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3 ACCESSORIES
Amron produces a series of accessories designed to operate with the AMCOM II chamber
communicators.
3.1 AMRON HEAVY-DUTY HEADSET - MODEL 2401-28
The Model 2401-28 is a heavy-duty headset with boom microphone. It comes equipped with
color-coded, dual banana plugs that mate directly to AMCOM diver communicators. It
includes a six foot (1.8 meter) cord.
3.2 AMRON STANDARD HEADSET - MODEL 2460-28
The Model 2460-28 is a light and comfortable headset designed for extended wear at an
economical price. It comes equipped with color-coded, dual banana plugs that mate directly
to AMCOM diver communicators as well as a spiral cord that can be extended up to 8 feet
(2.4 meters).
3.3 AMRON SINGLE EARPIECE HEADSET – MODEL 2460SM-28
The Model 2460SM-28 is a single earpiece version of the Model 2460-28 headset. The single
earpiece design allows the operator to hold conversations with other personnel without
having to remove the headset.
3.4 AMRON CHAMBER HEADSET - MODEL 2460-31R
The Model 2460-31R is a lightweight headset for use inside hyperbaric chambers. It comes
equipped with a spiral cord that can be extended up to 8 feet (2.4 meters) and 4-pin
connector that mates with chamber communication boxes.
3.5 AMRON CHAMBER EXTENSION CABLE – MODEL 2460-31R-25
The Model 2460-31R-25 provides a 25 foot (7.6 meters) extension cable to the Model 2460-
31R chamber headset.
3.6 AMRON REMOTE WALK-AND-TALK MODULE - MODEL 2822-28
Designed for 4-Wire (Full Duplex) applications, the Model 2822-28 provides the tender with
mobility around the dive site while maintaining communications with the diver. It comes
equipped with a small clip-on belt module that contains the connectors for the headset, and
25 feet (7.6 meters) of lightweight flexible cable. Custom cable lengths are available.
3.7 AMRON REMOTE PUSH-TO-TALK MODULE - MODEL 2821-28
Designed for 2-Wire applications, the Model 2821-28 provides the tender with mobility around
the dive site while maintaining communications with the diver. It comes equipped with a small
clip-on belt module that contains a Push-to-Talk switch, connector for the headset, and 25
feet (7.6 meters) of lightweight flexible cable. Custom cable lengths are available.

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3.8 AUDIO ADAPTOR CABLE - AMRON PART NUMBER 180-1000-00
Adapter cable is 6.5 feet (2 meter) long with two RCA Phono plugs that connect the auxiliary
audio input to a standard 3.5 mm stereo phone plug which mates to the headphone jack of
most common portable audio devices.
3.9 AMRON CHAMBER COMMUNICATION BOX – MODEL 3113
The Model 3113 provides communications between the operator and chamber occupants. It
includes a 15 Watt, 8 Ohm speaker for 2-Wire operation and includes a headset connector
for Full Duplex (4-Wire) communications mounted in a die cast zinc housing with a gray
epoxy powder coat.
3.10 AMRON CHAMBER COMMUNICATION BOX – MODEL 3113
The Model 3114 provides 2-Wire communications between the operator and chamber
occupants at an economical price. It includes a 5 Watt, 8 Ohm speaker with a 3 foot SJO 18
AWG cable mounted in a die cast zinc housing with a gray epoxy powder coat with stainless
steel front panel.
3.11 AMRON CHAMBER COMMUNICATION BOX – MODEL 3115
The Model 3115 Chamber Communication Box provides all the features of the Model 3113
along with a speaker on/off switch. This switch allows private communication when using a
headset. This box is approved for U.S. Navy chambers.
3.12 AMRON CHAMBER COMBO BOX – MODEL 3125
The Model 3125 is a combination Chamber Communication and Electrical Junction Box. It is
designed for inner lock functions and mounts directly to a chamber penetrator via a
penetrator adaptor bushing. It includes a chamber talk-back speaker for 2-Wire
communications, a speaker on/off switch, a headset jack for 4-Wire communications,
chamber temperature probe, sound powered phone and bracket, and power connection
circuit for chamber internal conditioning system and chamber scrubber.
3.13 AMRON CHAMBER COMBO BOX – MODEL 3126
The Model 3126 is a combination Chamber Communication and Electrical Junction Box. It is
designed for outer lock functions and mounts directly to a chamber penetrator via a
penetrator adaptor bushing. It includes a chamber talk-back speaker for 2-Wire
communications, a speaker on/off switch, a headset jack for 4-Wire communications and
sound powered phone and bracket.
3.14 AMRON CHAMBER JUNCTION BOX – MODEL 3127
The Model 3127 is an outside chamber junction box for use with the Models 3125 and 3126
Combo Boxes. It includes a 12-pin electrical penetrator, mounting adaptor and MS connector
that mates with the Model 3128 wiring harness.

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3.15 AMRON CHAMBER WIRING HARNESS – MODEL 3128
The Model 3128 Chamber Wiring Harness provides all the wiring connections to inner and
outer locks. It includes all the wiring for communicators.
3.16 AMRON CHAMBER ENTERTAINMENT SPEAKER – MODEL 3130
The Model 3130 Chamber Entertainment Speaker includes a 15 Watt, 8 Ohm music quality
speaker with Mylar impregnated cloth cone along with six 1/8 inch phone jacks for optional
headset. It is mounted in aluminum housing with epoxy powder coat and stainless steel
speaker grill.

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4 CONTROLS AND CONNECTIONS
Before using the 2820A-02 and 2820A-03 Chamber Communicator, the operator should be familiar
with all the operating controls and connections. While reading this manual, you will find capitalized
words such as PANEL SPEAKER. These words are to remind the reader that additional information
can be found in this section of the manual. All sections that describe features or functions for the
2820A-02 apply to the 2820A-03 unless otherwise noted.
4.1 OPERATOR AND LOCK CONTROLS
4.1.1 POWER SWITCH – This switch controls power to the unit.
4.1.2 SPEAKER SWITCH – This switch allows the tender to turn off the speaker. If the
tender is using a headset, it may be necessary to turn off the speaker in order to
prevent acoustic feedback.
4.1.3 PUSH-TO-TALK BUTTON – This switch allows the operator to talk to the chamber
occupants when operating in the 2-Wire mode. It is not necessary to use this
control in the Full Duplex (4-Wire) mode. When using Full Duplex mode, this
control allows the operator to interrupt the audio entertainment by muting when the
switch is pressed.

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4.1.4 OPERATOR VOLUME – This control sets the volume for the PANEL SPEAKER
and operator headset. Rotate this knob clockwise to increase the volume.
4.1.5 PANEL SPEAKER - The panel speaker features a waterproof speaker that allows
the tender to monitor conversations in the chamber. The volume level is controlled
by the OPERATOR VOLUME control and it can be turned off using the SPEAKER
SWITCH.
4.1.6 PANEL MIC – A front panel mounted microphone is located next to the PANEL
SPEAKER. It is used by the operator to communicate to chamber occupants. It is
active when the SPEAKER SWITCH is on and the PUSH-TO-TALK SWITCH is
pressed.
4.1.7 AC POWER INDICATOR – This LED is used by the operator to determine if the
communicator is being AC powered. When the LED is off, the communicator is
operating on battery power.
4.1.8 BATTERY CONDITION INDICATOR - This LED is used by the operator to
determine the available battery level. A steady green light means that the battery
level is sufficient to operate the unit. When the battery reaches approximately 3
hours of remaining life, the LED will start blinking at a rate of about once per
second. The exact amount of time is dependent on the age and condition of the
sealed lead acid battery. When the battery reaches its end-of-charge, the LED will
turn off. It is advised that the battery be connected to AC power as soon as
possible once the BATTERY CONDITION INDICATOR starts blinking.
4.1.9 INNER LOCK VOLUME – This control sets the volume for the inner lock speaker
and/or headsets. Rotate this knob clockwise to increase the volume.
4.1.10 INNER LOCK ON/OFF – This switch allows the chamber operator to turn off all
communications with the inner lock. It may be necessary to turn off the one or both
locks in order to prevent acoustic feedback if the chamber door is open.
4.1.11 OUTER LOCK VOLUME – This control sets the volume for the outer lock speaker
and/or headsets. Rotate this knob clockwise to increase the volume.
4.1.12 OUTER LOCK ON/OFF – This switch allows the chamber operator to turn off all
communications with the outer lock. It may be necessary to turn off the one or both
locks in order to prevent acoustic feedback if the chamber door is open.
4.1.13 ENTERTAINMENT VOLUME (2820A-03 only) – This control sets the volume for
the audio entertainment speakers. Rotate this knob clockwise to increase the
volume. The entertainment will be muted when the PUSH-TO-TALK SWITCH is
pressed at any volume level.

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4.2 OPERATOR CONNECTIONS
4.2.1 OPERATOR HEADSET - This is the dual banana jack (color-coded black) that
functions as both an output (earphone) and input (microphone) for the operator as
controlled by the PUSH-TO-TALK SWITCH and PUSH-TO-TALK JACK. With this
connection, the operator can be wired in either 2-Wire or Full Duplex (4-Wire)
mode regardless of the mode used for the chamber.
The operator is connected in 2-Wire mode by stacking both the earphone (black) and
microphone (red) banana plugs into this OPERATOR HEADSET jack as shown in the
wiring diagram in section 4.4. The chamber does not have to be connected in 2-Wire
mode if the operator is in 2-Wire mode. In order to talk to the chamber occupants, the
operator must use either the PUSH-TO-TALK SWITCH or PUSH-TO-TALK JACK.
Since the headset microphone is not active until one of the push-to-talk methods is
used, there is no chance for acoustic feedback to occur and outside conversation or
noise is not transmitted to chamber and the PANEL SPEAKER can be left on. This may,
for some situations, make for a better overall communication experience. If the operator
requires more mobility, the Amron Model 2821-28 Remote Push-to-Talk Module can be
used to extend the headset cable. It includes a push-to-talk button on a clip-on belt
module and comes standard with 25 feet (7.6 meters) of cable (custom cable lengths
are available).
To connect the operator in the Full Duplex (4-Wire) mode, connect the earphone (black)
banana plug of the headset to this jack and the microphone (red) to the OPERATOR
MICROPHONE jack (red) as shown in the wiring diagram in section 4.4. In this mode,
the operator does not have to use the PUSH-TO-TALK SWITCH to communicate with
chamber occupants who are also connected in the Full Duplex (4-Wire) mode. This
configuration can be used even if the chamber is connected in 2-Wire mode. In that
situation, the tender is required to use the PUSH-TO-TALK SWITCH or PUSH-TO-
TALK JACK.
The headset microphone is always active which means that there can be acoustic
feedback between the PANEL SPEAKER and the microphone if the operator is near the
communicator. To prevent this, the PANEL SPEAKER can be turned off using the
SPEAKER SWITCH. Another option is to move the operator away from the
communicator by using the Amron Model 2822-28 Walk-and-Talk Module accessory.
This allows the operator to communicate while other members of the crew listen using
the PANEL SPEAKER. This module comes with 25 feet (7.6 meters) of cable (custom
cable lengths are available).
The operator may also use the included Amron Model 2405-28 Push-to-Talk
Microphone. This microphone comes with two color-coded banana plugs. The black
plug goes into the OPERATOR HEADSET jack and the yellow plug goes in the PUSH-
TO-TALK JACK as shown in the wiring diagram in section 4.5. To communicate with the
chamber occupants, the operator presses the button on the side of the microphone.
There is no chance of acoustic feedback since the PANEL SPEAKER is cut-off when
the operator uses the microphone. When using the Push-to-Talk Microphone, the
SPEAKER SWITCH must be turned on in order to hear the chamber.

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4.2.2 OPERATOR MICROPHONE - This is a dual banana jack (color-coded red) that
functions as the microphone input from the operator's headset. It is only used if the
operator is in Full Duplex (4-Wire) mode.
4.2.3 PUSH-TO-TALK JACK -This is a dual banana jack (color-coded yellow) that
allows for remote keying of the push-to-talk function of the communicator. The
difference between using the PUSH-TO-TALK JACK and PUSH-TO-TALK
SWITCH is that the switch allows the operator to communicate using the PANEL
MIC. If both are used at the same time, the PANEL MIC is active. This allows a
crew member to talk to the chamber occupants using the PANEL MIC even if the
operator is away from the communicator using the Remote Push-to-Talk Module in
2-Wire mode.
4.2.4 RECORDER OUTPUT - This is a single RCA Phono jack (color-coded black) that
provides a transformer isolated of both the operator and chamber communications.
It is designed to drive the standard line-level inputs of audio or video recorders with
input impedances as low as 600 Ohms.
4.3 BACK PANEL CONNECTIONS
4.3.1 MS CONNECTOR - There is a 14 pin MS Style connector located on the back
panel that provides the electrical connection to the chamber. The pin functions are
shown in the following table:
PIN NUMBER FUNCTION
K
Entertainment Speaker High (4003E Only)
L
Entertainment Speaker Low (4003E Only)
E
Outer Lock Microphone High
F Outer Lock Microphone Low
G Outer Lock Earphone High
H Outer Lock Earphone Low
A Inner Lock Microphone High
B
Inner Lock Microphone Low
C
Inner Lock Earphone High
D
Inner Lock Earphone Low
I
External Power +
J
External Power -
4.3.2 ENTERTAINMENT SPEAKER (2820A-03 only) - This connection is only available
on the 2820A-03. It is routed to a separate entertainment speaker, such as the
Amron Model 3130, usually located in the Inner Lock.
4.3.3 OUTER MICROPHONE - This connection functions as both an output (earphone)
and input (microphone) for the outer lock occupants as controlled by the PUSH-
TO-TALK SWITCH and PUSH-TO-TALK JACK. Using this connection, the
chamber can be wired in either 2-Wire or Full Duplex (4-Wire) mode regardless of
the mode used for the operator.

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To connect the chamber in Full Duplex (4-Wire) mode, connect the chamber
headset microphone pin to this connection as shown in section 4.6.
To connect the chamber in 2-Wire mode, connect the talk-back speaker, such as
the Amron Model 3114 Chamber Speaker Box to this connection. You can have a
mixed Full Duplex and 2-Wire by having both a talk-back speaker and headset jack
by using the Amron Model 3115 Chamber Communicator Box as shown in section
4.6.
4.3.4 OUTER EARPHONE - This connection functions as the output for the chamber
headset earphone. It is only used when the chamber is in Full Duplex (4-Wire)
mode.
4.3.5 INNER MICROPHONE - This connection has the same function as the OUTER
MICROPHONE but for the inner lock.
4.3.6 INNER EARPHONE - This connection has the same function as the OUTER
EARPHONE but for the inner lock.
4.3.7 EXTERNAL POWER - The communicator can be powered using an external
battery or power supply via this connection. The input voltage must be between 9
and 16 VDC and must be able to supply a peak current of 3 Amps for proper
operation. The following warning should be followed when using the EXTERNAL
POWER connection. A minimum wire size of 18 AWG and maximum wire run of 3
feet (1 meter) is recommended.
4.3.8 ENTERTAINMENT AUDIO INPUT (2820A-03 ONLY)
This is a set of two RCA Phone jacks (color-coded red and white) that provides a
means to connect an external audio signal for chamber occupant’s entertainment.
Although this input will accept a stereo audio source, it will be converted into a
monaural signal before going to the chamber. The earphone output of most MP3
players can be connected to this input using an adaptor cable like the Amron Audio
Adaptor Cable (Amron Part Number 180-1000-00).
4.3.9 AC POWER INLET
This is a standard IEC type C14 AC Power Inlet. The communicator is shipped with
a NEMA 5-15 power cable but the communicator will accept AC input voltages from
90-264 VAC with a frequency 47-440 Hz.
WARNING!
The EXTERNAL POWER input can be used to recharge the 2820A-02 &
2820A-03 rechargeable sealed lead acid battery. If you use an external
power supply, the maximum voltage needs to be limited to 9-16 Volts.

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4.4 DRAWING, OPERATOR HEADSET CONNECTIONS

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4.5 DRAWING, PUSH-TO-TALK CONNECTIONS

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4.6 DRAWING, 2820A-02 & 2820A-03 TO CHAMBER WIRING DIAGRAM

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5 OPERATION
Before operating the communicator, it should be securely mounted to the panel. The panel cutout
dimensions are shown in section 8.3.
5.1 CHARGING THE BATTERY
The Models 2820A-02 and 2820A-03 are supplied with a sealed lead acid back up battery. To
charge the battery, insert the AC power cord to the AC inlet located on the back of the
communicator. The internal battery charger is able to operate on AC input voltages from 90-
264 VAC with a frequency 47-440 Hz. without the user having to make any adjustments.
The internal battery charger is designed to charge the battery in float mode so the charger
can be left on indefinitely, without damage, to ensure the battery is fully charged and the unit
is ready to use. A fully discharged battery will take approximately 10 hours to reach full
charge (depending on the age of the battery and the surrounding temperature). To ensure
maximum service life, the battery should be fully charged at least once every six months.
The operating time for a fully charged battery is approximately 45 hours. The exact operating
time depends on the age of the battery and the ambient temperature. The sealed lead acid
battery used in the communicator has a service life of 300 full charge/discharge cycles or 3
years. The BATTERY CONDITION INDICATOR will start to blink when the battery has
approximately 3 hours operating time remaining. To maximize the service life, the battery
should be recharged as soon as possible after the indicator starts to blink. When the battery
reaches the full discharge state, the BATTERY CONDITION INDICATOR will turn off and the
communicator will shut down.
5.2 INITIAL POWER ON - BATTERY CONDITION CHECK
Turn all the volume controls to minimum and turn on the POWER SWITCH. The state of the
battery is shown on the BATTERY CONDITION INDICATOR as follows:
•STEADY GREEN - the battery is good and has more than 30% remaining life.
•BLINKING GREEN - the battery is low and has less than 30% remaining life.
•OFF or NO LIGHT - the battery is depleted and needs to be changed/recharged before
use.
•STEADY RED - light indicates the battery voltage is too low to operate the unit.
Communication should stop.
The BLINKING GREEN light provides a warning that the battery is low and should be
changed or recharged before starting the dive operation. When the indicator starts BLINKING
GREEN during dive operations, there is, depending on age of the battery and the ambient
temperature, approximately 24 hours of remaining battery life. This should be sufficient time
to safely complete dive operations. A battery that has not been used for a long period of time
will exhibit a higher voltage than the actual charge state. This is known as surface charge and
will quickly dissipate once the unit is turned on. It is recommended that the unit be left on for
5 minutes before relying on the BATTERY CONDITION INDICATOR.

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5.3 OPERATING ON AC POWER
The communicator is normally operated on AC power using the internal battery as backup in
case of power failures. The internal power supply is designed with medical grade electrical
isolation to prevent possible injuries due to electrical leakage. If external power is supplied
through the EXTERNAL POWER connection on the MS connector, it should have the same
type of isolation to prevent possible electrocution.
5.4 MODES OF OPERATION
The Models 2820A-02 & 2820A-03 have the ability to operate in either 2-Wire or Full Duplex
(4-Wire). Both the chamber and the operator can be connected in either mode and a
combination of modes can be used. If either the chamber or the operator is wired in 2-Wire
mode, the operator must use a push-to-talk, either the PUSH-TO-TALK SWITCH or PUSH-
TO-TALK JACK, when talking to the chamber. Using either push-to-talk method will cut off
the entertainment speaker.
2-Wire communication is defined as a single communication path, normally the chamber is
the priority signal path – operator listens to chamber. Signal reversing is accomplished by
pushing the PUSH-TO-TALK SWITCH – chamber hears the operator. Since only one person
can talk at a time, there is a level of discipline that goes with using 2-Wire mode in order to
obtain clear communications. One advantage of 2-Wire is that the operator’s microphone is
not active unless one of the two push-to-talk controls, PUSH-TO-TALK SWITCH or PUSH-
TO-TALK JACK, are active. This eliminates any possible acoustic feedback between the
operator's microphone and the PANEL SPEAKER. It also prevents noise from the outside
reaching the chamber occupants and allows the operator to communicate with other crew
members without involving the chamber occupants.
4-Wire (Full Duplex) communication is defined as a dual communication path, a signal path
(a pair of wires) for up-link and a signal path (a pair of wires) for down link. A common
example of Full Duplex communication is the telephone. Full Duplex (4-Wire) has the
advantage of natural communication without having to use the PUSH-TO-TALK SWITCH.
This keeps the operator's hands free to perform other task. It does not require the same level
of discipline to achieve clear communications that 2-Wire does. It has the advantage that
neither the chamber occupants nor the operator are cut off when the other is talking. 4-Wire
does require the chamber occupant, as well as the operator, to wear headsets.
5.5 SETTING THE VOLUME CONTROLS
5.5.1 2-WIRE MODE
Turn power switch to ON, turn speaker switch to ON, and adjust all volume controls
to mid-scale. The operator has to depress PUSH-TO-TALK BUTTON in order to
the chamber occupants. Operator and chamber occupants talk to each other while
the operator adjusts volume controls. Adjusting the lock volumes is easier if the
other LOCK ON/OFF switch is turned off.
OPERATOR VOLUME – While chamber occupant(s) are talking, the operator
adjusts this volume control to a comfortable hearing level at the PANEL SPEAKER
or operator headset.

2820A-02 & 2820A-03 CHAMBER COMMUNICATOR USER MANUAL
2820A-02-UM
REV 1.0
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LOCK VOLUME – While operator is talking into the PANEL MIC or hand-held
microphone and depressing PTT switch, the operator adjusts this volume control to
a comfortable level.
5.5.2 4-WIRE MODE
Turn power switch to ON; turn speaker switch to OFF; adjust volume controls to
mid-scale. The operator and chamber occupants use headsets. While talking to
each other, the operator adjusts volume controls as below:
OPERATOR VOLUME – While the chamber occupant is talking, the operator
adjusts this volume control to a comfortable hearing level.
LOCK VOLUME – While the operator is talking, the operator adjusts this volume
control to a comfortable level for the chamber occupants. This should be conducted
on each lock individually with the other lock turned off during adjustment process.