Amron 2820A User manual

User Manual
For
Amron International, Inc.
Model 2820A-XX & 2825A-XX Series
Portable Two Diver 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© 2020 Amron International, Inc.

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TABLE OF CONTENTS
1INTRODUCTION AND SPECIFICATIONS ..........................................................................................1
1.1 INTRODUCTION...........................................................................................................................1
1.2 SPECIFICATIONS ........................................................................................................................1
1.3 BATTERY LIFE.............................................................................................................................2
1.4 MATERIALS, WEIGHTS & DIMENSIONS....................................................................................2
2OPTIONS AND ACCESSORIES..........................................................................................................3
2.1 OPTIONS......................................................................................................................................3
2.2 ACCESSORIES ............................................................................................................................3
3CONTROLS AND CONNECTIONS......................................................................................................5
3.1 TENDER CONTROLS & CONNECTIONS ...................................................................................5
3.2 DIVER CONTROLS & CONNECTIONS.......................................................................................8
3.3 HELIUM SPEECH UNSCRAMBLER (DSP3) CONTROLS..........................................................9
3.4 WIRELESS TENDER (28B) CONTROLS...................................................................................10
3.5 DRAWING, 2-WIRE CONNECTIONS.........................................................................................11
3.6 DRAWING, FULL DUPLEX (4-WIRE) CONNECTIONS.............................................................12
3.7 DRAWING, OPERATOR CONNECTIONS, HAND HELD MICROPHONE................................13
3.8 DRAWING, OPERATOR CONNECTIONS, HEADSET..............................................................14
4OPERATION.......................................................................................................................................15
4.1 BATTERY CHARGING ...............................................................................................................15
4.2 BATTERY CONDITION ..............................................................................................................16
4.3 BATTERY INSTALLATION.........................................................................................................16
4.4 MODES OF OPERATION...........................................................................................................16
4.5 VOLUME CONTROLS (2-WIRE)................................................................................................18
4.6 VOLUME CONTROLS FULL DUPLEX (4-WIRE).......................................................................18
4.7 HELIUM SPEECH UNSCRAMBLER OPTION...........................................................................19
5MAINTENANCE AND TROUBLESHOOTING...................................................................................23
5.1 FULL DUPLEX (4-WIRE) CHECK ..............................................................................................23
5.2 2-WIRE CHECK..........................................................................................................................23
5.3 GENERAL MAINTENANCE........................................................................................................24
5.4 RECOMMENDED MAINTENANCE SCHEDULE.......................................................................24
5.5 TROUBLESHOOTING................................................................................................................26
6DRAWINGS ........................................................................................................................................29
6.1 PARTS IDENTIFIER, MODEL 2820A-11 WEATHER RESISTANT AC POWER MODULE......30
6.2 PARTS IDENTIFIER, MODEL 2825A-11 WEATHER RESISTANT AC POWER MODULE......31
6.3 PARTS IDENTIFIER, MODEL 2825A-12 WEATHER RESISTANT AC POWER MODULE &
DSP3 HELIUM SPEECH UNSCRAMBLER ...............................................................................32
6.4 PARTS IDENTIFIER, MODEL 2825A-13 WEATHER RESISTANT AC POWER MODULE & 28B
WIRELESS TENDER..................................................................................................................33

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7PARTS LISTS.....................................................................................................................................34
7.1 PARTS LIST FOR 282XA-XX SERIES FRONT PANEL ASSEMBLIES.....................................34
7.2 PARTS LIST, MODEL 2820A-11, WEATHER RESISTANT AC POWER MODULE .................35
7.3 PARTS LIST, MODEL 2825A-11, WEATHER RESISTANT AC POWER MODULE .................35
7.4 PARTS LIST, MODEL 2825A-12, WEATHER RESISTANT AC POWER MODULE & DSP3
HELIUM UNSCRAMBLER OPTION...........................................................................................35
7.5 PARTS LIST, MODEL 2825A-13, WEATHER RESISTANT AC POWER MODULE & 28B
WIRELESS TENDER OPTION...................................................................................................36
7.6 PARTS LIST, 2820-302 CASE ASSEMBLY WITH POWER ENTRY MODULE ........................36
7.7 28XXA-FS-02 FIELD SPARES KIT FOR 2820A, 2825A............................................................36
8LIMITED WARRANTY AND SERVICE POLICY................................................................................38

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1 INTRODUCTION AND SPECIFICATIONS
1.1 INTRODUCTION
Congratulations on purchasing the most advanced and powerful portable communicator in
the diving industry! Our engineering team has integrated the latest in digital advancements to
produce the industry’s most intelligible and reliable diver communicators. Our built-in quality
that Amron is known for makes the 2820A & 2825A series the most versatile and durable
communicators anywhere in the world!
The AMCOM II Series is a family of full-featured hard-wired, two-diver communicators. The
AMCOM II is offered in two basic versions. The units are identical except the Model 2825A
series has independent microphone and earphone volume controls for each diver and the
tender. The 2820A series has a single earphone volume control for diver’s volume (down-
link) and a single volume control for the tender (up-link).
All models come standard with a built-in internal charger and can be operated from either a
90-264 VAC, internal 12 VDC battery, or an external 12 VDC power source.
All communicators are supplied with an outdoor weather resistant AC power entry module
located on the case, and country specific locking AC power cord of your choice.
There are options available to fit your application such as DSP3 Helium Speech Unscrambler
and 28B Wireless Tender.
The 2820A-XX and 2825A-XX series has the ability to operate in the 2-Wire and Full Duplex
(4-Wire) mode, as well as both modes being used simultaneously. Full Duplex (4-Wire) mode
is required when using the Inhalation Noise Reduction or Wireless Tender features.
Only Amron offers Microphone Auto Detection that identifies the type of microphone each
diver is using and automatically adjusts for optimum performance. This portable diving
communicator has the ability to work with both dynamic and pre-amplified microphones in
either 2-Wire or 4-Wire modes.
1.2 SPECIFICATIONS
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, 50-60 Hz
Sensitivity (Input) .............................................................................................................0.5 mV
Output Power (RMS @ 4 Ohm Load, 12 VDC) ..................................................10 Watts Audio

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1.3 BATTERY LIFE
Model 2820A-11 ........................................................................................................... 45 Hours
Model 2825A-11 .......................................................................................................... 45 Hours
Model 2825A-12 ........................................................................................................... 31 Hours
Model 2825A-13 ........................................................................................................... 32 Hours
1.4 MATERIALS, WEIGHTS & DIMENSIONS
Front Panel...............................................................................Stainless Steel, Powder Coated
Enclosure................................................................................High Impact UV Resistant Plastic
Enclosure Color.................................................................................Bright International Yellow
Length ..........................................................................................................14.5 In. (36.8 Cm)
Width ............................................................................................................9.0 In. (22.9 Cm)
Height ..........................................................................................................10.0 In. (25.4 Cm)
Model 2820A-11 with AC Power Module and Internal Charger ................. 16.25 Lbs. (7.37 Kg)
Model 2825A-11 with AC Power Module and Internal Charger ................. 16.95 Lbs. (7.69 Kg)
Model 2825A-12 with DSP3 Helium Speech Unscrambler Option............. 17.25 Lbs. (7.82 Kg)
Model 2825A-13 with 28B Wireless Tender Option ................................... 17.15 Lbs. (7.78 Kg)

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2 OPTIONS AND ACCESSORIES
The following options are available to customize the 2825A Series AMCOM communicators. Options
have to be ordered at the time of purchase or the communicator has to be returned to AMRON for the
option to be installed.
2.1 OPTIONS
-11 AC POWER WITH INTERNAL CHARGER
Commercial styletwo diver rechargeable communicator with binding posts comes
standard with AC power module, country specific locking power cord, and hand
held microphone.
2.1.1 -12 HELIUM SPEECH UNSCRAMBLER (HSU)
The communicator has all the features of the Model 2825A-11 plus Amron’s DSP3
Helium Speech Unscrambler (HSU) using the state-of-the-art Digital Signal
Processor (DSP) technology to correct raw helium speech into clear, intelligible
voice. This option includes a complex noise reduction filter to improve
communications in situations with high background noise levels.
-13 WIRELESS TENDER OPTION
The communicator has all the features of the Model 2825A-11 plus the wireless
tender option. The wireless option includes communicator master module, remote
module, remote module charger, remote wireless tender headset, remote ultra-light
headset, and carrying case. The wireless tender option allows the tender freedom
to move around up to 200 feet from the communicator. The wireless tender option
does require the divers to be wired in Full Duplex (4-Wire) mode.
2.2 ACCESSORIES
The following accessories are available for the AMCOM III communicator. Accessories can
be ordered at any time.
2.2.1 Item No. 2401-28 AMRON HEAVY-DUTY HEADSET (Dual Ear Muffs)
The Model 2401-28 is a high quality heavy-duty Telex headset with dual ear muffs
and boom microphone. It has superior sound quality and comes equipped with
color-coded dual banana plugs, 6-foot (1.8-meter) cord, and mates directly to
communicator.
2.2.2 Item No. 2401SM-28 AMRON HEAVY-DUTY HEADSET (Single Ear Muff)
The Model 2401SM-28 is a high quality heavy-duty Telex headset with a single ear
muff and boom microphone. It has superior sound quality and comes equipped with
color-coded dual banana plugs, 6-foot (1.8-meter) cord, and mates directly to
communicator.
2.2.3 Item No. 2460-28 AMRON STANDARD HEADSET (Dual Ear Muffs)
The Model 2460-28 is a light and comfortable headset with dual ear muffs and
designed for extended wear at an economical price. It comes equipped with color-
coded, dual banana plugs that mate directly to AMCOM diver communicators. The
spiral cord can extend up to 8 feet (2.4 meters).

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2.2.4 Item No. 2460SM-28 AMRON STANDARD HEADSET (Single Ear Muff)
The Model 2460-28 is a light and comfortable headset with a single ear muff and
designed for extended wear at an economical price. It comes equipped with color-
coded, dual banana plugs that mate directly to AMCOM diver communicators. The
spiral cord can extend up to 8 feet (2.4 meters).
2.2.5 Item No. 2490-28 NOISE REDUCTION HEADSET (Dual Ear Muffs)
The Model 2490-28 Active Noise Reduction (ANR) headset isolates and reduces
topside noise in loud environments dramatically, allowing the tender and divers to
communicate more clearly and comfortably with increased intelligibility.
Amron’s Active Noise Reduction Headset features two key technologies,
unmatched active noise reduction and unique dynamic noise cancelling
microphone. The proprietary electronic circuitry design shapes and equalizes
incoming audio signals to provide a clean full sound quality that enhances
intelligibility of the intercom audio.
The headset comes equipped with dual ear muffs, color-coded dual banana plugs,
6-foot (1.8-meter) cord, and mates directly to the communicator.
2.2.6 Item No. 2490SM-28 NOISE REDUCTION HEADSET (Single Ear Muff)
The Model 2490SM-28 Active Noise Reduction (ANR) headset isolates and
reduces topside noise in loud environments dramatically, allowing the tender and
divers to communicate more clearly and comfortably with increased intelligibility.
Amron’s Active Noise Reduction Headset features two key technologies,
unmatched active noise reduction and unique dynamic noise cancelling
microphone. The proprietary electronic circuitry design shapes and equalizes
incoming audio signals to provide a clean full sound quality that enhances
intelligibility of the intercom audio.
The headset comes equipped with a single ear muff, color-coded dual banana
plugs, 6-foot (1.8-meter) cord, and mates directly to the communicator.
2.2.7 Item No. 2405-28 AMRON PUSH-TO-TALK MIC
The Model 2405-28 is a dynamic hand-held push-to-talk microphone that provides
excellent sound quality to the diver. It comes equipped with a spiral cord that can
extend up to 6 feet (1.8 meters).
2.2.8 Item No. 2405NC-28 AMRON NOISE CANCELLING PUSH-TO-TALK MIC
The Model 2405-28 is a noise cancelling hand-held push-to-talk microphone that
provides excellent sound quality to the diver. It comes equipped with a spiral cord
that can extend up to 6 feet (1.8 meters).
2.2.9 Item No. 2822-28 AMRON REMOTE WALK-AND-TALK MODULE

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Designed for Full Duplex (4-Wire) 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 upon request.
2.2.10 Item No. 2821-28 AMRON REMOTE PUSH-TO-TALK MODULE
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 upon request.
2.2.11 Item No. 190-0650-01 AMRON WIRELESS TENDER HEADSET (Single Ear Muff)
A single ear muff headset that is compatible with the 28B Wireless Tender option.
Additional headsets can be ordered to allow other crew members, supervisors,
crane operators, etc. to monitor the conversation.
2.2.12 Item No. 190-0650-02 AMRON WIRELESS TENDER HEADSET (Dual Ear Muffs)
Dual ear muffs headset that is compatible with the 28B Wireless Tender option.
Additional headsets can be ordered to allow other crew members, supervisors,
crane operators, etc. to monitor the conversation.
3 CONTROLS AND CONNECTIONS
Before using the AMCOM II series diver communications system, you should familiarize yourself with
its operating controls and connections. Improper use of controls and connections will deprive the user
of the full benefits of this communication system.
3.1 TENDER CONTROLS & CONNECTIONS
3.1.1 AC POWER LED to identify the presence of AC power. When the communicator is
plugged into AC power, the Green LED will be on regardless if the communicators
POWER SWITCH is on or off.
3.1.2 POWER SWITCH –controls power to the communicator.
3.1.3 SPEAKER 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.
3.1.4 PUSH-TO-TALK (ALL DIVERS) –allows the tender to talk to all the divers when
operating in the 2-Wire mode. It is not necessary to use this control in the Full
Duplex (4-Wire) mode and tender wearing a headset.
3.1.5 TENDER MICROPHONE VOLUME (2825A series only) – controls the volume level
for the tender's microphone and/or PANEL MICROPHONE. Rotate knob clockwise
to increase the tender’s volume to all the divers.

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3.1.6 TENDER EARPHONE VOLUME –controls the volume level for the tender's
earphone and/or PANEL SPEAKER. Rotate this knob clockwise to increase the
volume from all the divers
3.1.7 BATTERY CONDITION INDICATOR – a steady GREEN LED light indicates
battery charge level is good. Blinking GREEN LED light indicates battery charge
level is at a low level with less than 3 hours of running time available. Steady RED
LED light indicates battery charge level is below the level necessary to guarantee
proper operation.
WARNING: When BATTERY CONDITION INDICATOR is steady RED LED light,
the batteries should be replaced or recharged immediately.
3.1.8 PANEL SPEAKER – is a waterproof acoustic horn speaker that allows the tender
to listen to the divers. The volume level is controlled by the EARPHONE VOLUME
controls and it can be turned off using the SPEAKER SWITCH.
3.1.9 PANEL MICROPHONE – is a water-resistant condenser microphone that allows
the tender to talk to the divers using the PUSH-TO-TALK BUTTONS. The volume
level is controlled by the MICROPHONE VOLUME controls. The PANEL
MICROPHONE is muted when the SPEAKER SWITCH is turned off.
WARNING: Do not plug or cover the PANEL MICROPHONE hole. This may
reduce or eliminate the tender-to-diver communications, and possibly
damage the microphone.
3.1.10 TENDER HEADSET JACKS (BLACK) –are dual banana jacks (color-coded black)
that functions as both an output (earphone) and input (microphone) for the tender
as controlled by the PUSH-TO-TALK BUTTON and PUSH-TO-TALK JACK. Using
this connection, the tender can be wired in either 2-Wire or Full Duplex (4-Wire)
mode regardless of the mode used for the diver.
To connect the tender 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
TENDER MICROPHONE jack (red) as shown in wiring diagram section 3.6. In this
mode, the tender does not have to use the PUSH-TO-TALK BUTTON to
communicate with a diver who is also connected in the Full Duplex (4-Wire) mode.
This configuration can be used even if the diver is connected in 2-Wire mode. In
that situation, the tender is required to use the PUSH-TO-TALK BUTTON 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 tender is near
the communicator. To prevent this, the PANEL SPEAKER can be turned off using
the SPEAKER SWITCH. Another option is to move the tender away from the
communicator by using the Amron Model 2822-28 Walk-and-Talk Module
accessory. This allows the tender to communicate while other members of the
surface crew listen using the PANEL SPEAKER. This module comes with 25 feet
(7.6 meters) of cable (custom cable lengths are available).

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The tender can also be connected in 2-Wire mode by stacking both the earphone
(black) and microphone (red) banana plugs into this jack as shown in wiring
diagram section 3.5. The diver does not have to be connected in 2-Wire mode if
the tender is in 2-Wire mode. In order to talk to the diver, the tender must use
either the PUSH-TO-TALK BUTTON 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 surface conversation or noise is not
transmitted to diver and the PANEL SPEAKER can be left on. This may, for some
situations, make for a better overall diving experience. If the tender requires more
mobility at the dive site, 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).
The tender may also use the optional Amron Model 2405-28 Push-to-Talk
Microphone. This microphone comes with two color-coded banana plugs. The
black plug goes into the TENDER HEADSET jack and the yellow plug goes in the
PUSH-TO-TALK JACK as shown in wiring diagram section 3.5. To communicate
with the diver, the tender 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
tender uses the microphone. When using the Push-to-Talk Microphone, the
SPEAKER SWITCH must be turned on in order to hear the diver.
3.1.11 TENDER MICROPHONE JACKS (RED) – are dual banana jacks (color-coded red)
that functions as the microphone input from the tender's headset. It is only used if
the tender is in Full Duplex (4-Wire) mode.
3.1.12 PUSH-TO-TALK JACKS (YELLOW) – are dual banana jacks (color-coded yellow)
that allows for remote keying of the push-to-talk function of the communicator. It is
use by the Push-To-Talk Microphone (Amron Model 2405-28) and the Remote
Walk-And-Talk Module (Amron Model 2822-28).
The difference between using the PUSH-TO-TALK JACK and PUSH-TO-TALK
SWITCH is that the switch allows the tender to communicate using the PANEL
MICROPHONE. If both are used at the same time, the PANEL MICROPHONE is
active. This allows another crew member to talk to the diver using the PANEL
MICROPHONE even if the tender is away from the communicator using the
Remote Push-to-Talk Module in 2-Wire mode.
3.1.13 EXTERNAL BATTERY JACKS – The communicator can be powered using an
external battery or power supply using color coded TIP jacks. The red TIP jack is
the positive power input and the black is the negative power input. The input
voltage must be between 9 and 15 VDC and must be able to supply a peak current
of 3 Amps for proper operation. It is recommended that the minimum wire gauge
size to be 18 AWG or larger with a maximum length of 3 feet (1 meter).
WARNING: If you use an external power supply, the maximum voltage cannot
exceed 16 Volts.

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3.1.14 AUDIO OUT – is a single RCA Phono jack (color-coded black) that provides a
transformer isolated of both the diver and tender communications. It is designed to
drive the standard line-level inputs of audio or video recorders with input
impedances as low as 600 Ohms.
3.1.15 SEALED AC POWER ENTRY MODULE – is located on the right side of the case
and outdoor rated offering IP 65 protection to the communicator and IP54
protection to the cord connection. The internal battery charger has a universal
input AC voltage range from 90-264 VAC over a frequency range from 50-60 Hz.
3.1.16 COUNTRY SPECIFIC LOCKING AC POWER CORD – is supplied with every
communicator and country type is selected at time of order. The outdoor rated
power cord locks into the weather resistant AC Power Entry Module located on the
side of the communicators case, offering IP 54 protection to the cord connection.
3.2 DIVER CONTROLS & CONNECTIONS
DIVER EARPHONE VOLUME – has separate earphone volume controls for each diver. This
allows the tender to adjust the optimum earphone volume level for each individual
diver.
3.2.1 DIVER MICROPHONE VOLUME – has separate microphone volume controls for
each diver. This allows the tender to adjust the optimum microphone volume level
for each individual diver.
3.2.2 DIVER PUSH-TO-TALK SWITCH – provided for each diver and used only in the 2-
Wire Mode. This function allows the tender to carry on a private conversation with
only the diver(s) selected.
3.2.3 DIVER MICROPHONE CONNECTION (RED) – is a dual 5-way binding post jack
(color-coded red) that functions as both an output (earphone) and input
(microphone) for the diver as controlled by the PUSH-TO-TALK BUTTON and
PUSH-TO-TALK JACK. Using this connection, the diver can be wired in either 2-
Wire or Full Duplex (4-Wire) mode.
To connect the diver in 2-Wire mode, connect both the diver microphone and
earphone to this jack. If the diver umbilical uses banana plugs, simply stack both
plugs into this jack as shown in the 2-Wire wiring diagram section 3.5. In this mode,
the diver microphone will be active and heard on tender headset and/or PANEL
SPEAKER unless the PUSH-TO-TALK BUTTON or PUSH-TO-TALK JACK is used.
When a pre-amp microphone is used in the 2-Wire mode setup, it is required to
have special speakers supplied only by Amron. Contact Amron for more
information.
To connect the diver in Full Duplex (4-Wire) mode, connect the diver microphone to
this jack and the diver earphone the DIVER EARPHONE jack simply stack both
plugs into this jack as shown in the 2-Wire wiring diagram section 3.6. The diver
can use this mode even if the tender is wired in 2-Wire mode.

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3.2.4 DIVER EARPHONE CONNECTION (BLACK) – is a dual 5-way binding post jack
(color-coded black) that functions as the output for the diver's earphone. It is only
used when the diver is in Full Duplex (4-Wire) mode.
3.3 HELIUM SPEECH UNSCRAMBLER (DSP3) CONTROLS
The controls for the DSP3 Helium Speech Unscrambler (HSU) are located in the options
panel on the right side of the front panel as shown below.
3.3.1 ON/OFF SWITCH – Allows the selection of air (OFF) or helium (ON) operation. In
the OFF position, the divers’ microphone signal bypasses the HSU. In the ON
position, the microphone signals are routed to the HSU and the tender can adjust
the controls as necessary.
3.3.2 TREBLE BOOST – Selects the amount of gain added to the High Frequency (HF)
portion of the divers’ microphone signals. This compensates for the HF drop-off in
the sensitivity of most microphones. The TREBLE BOOST feature allows for
optimum frequency enhancement and improved intelligible speech from the diver’s
voice.
3.3.3 DEPTH CONTROL – Selects the amount of frequency correction performed by the
HSU to produce intelligible speech. This control uses a multi-turn potentiometer
and is equipped with a turn counting knob and lock. Once the desired setting is
reached, the lock can be used to prevent accidental changes to this control.
3.3.4 NOISE REDUCTION FILTER – The Noise Reduction Filter (NRF) uses a complex
Digital Signal Processor algorithm based on a statistical-model of human voice
activity to capture the background noise and reduce it without affecting the divers’
speech. The noise level can be reduced by up to 17dB.

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3.4 WIRELESS TENDER (28B) CONTROLS
3.4.1 BASE STATION ON/OFF/VOLUME – control is located on the bottom right side of
the Base Station. It turns on and off the power to the Wireless Tender Base
Station and adjusts the volume level by rotating the knob in either direction.
3.4.2 BASE STATION CHANNELS 1 & 2 – programming buttons are located on the rear
side of the base-station. Up to 3 remote headsets can be programed per channel.
3.4.3 WIRELESS REMOTE HEADSET ON/OFF & VOLUME – controls are located on
the headset ear muff. The top button powers on and off the headset, and the
up/down arrows control the headset volume.
3.4.4 RECHARGEABLE BATTERY – is located on the opposite ear muff from the
controls and boom mic.

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3.5 DRAWING, 2-WIRE CONNECTIONS

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3.6 DRAWING, FULL DUPLEX (4-WIRE) CONNECTIONS

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3.7 DRAWING, OPERATOR CONNECTIONS, HAND HELD MICROPHONE

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3.8 DRAWING, OPERATOR CONNECTIONS, HEADSET

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4 OPERATION
The AMCOM II portable diver communicators are supplied in a durable yellow enclosure. To
open the enclosure, release the two latches on the front of the unit and raise the lid. The lid of
the communicator can be removed by sliding the lid to the side.
The AMCOM II panels are graphically divided into sections starting from left to right: Tender
Controls, Diver Controls, and Options. Items within these areas are functions or controls
relating to the Tender, Diver(s) or Optional items.
WARNING: When operating your Amron Diver Communicator from AC mains, it is
critical to use a Ground Fault Circuit Interrupter (GFCI) and/or isolation transformer for
tender and diver safety. Surges and spikes are common on AC lines found onboard
ships, from local generators, or at the end of a long extension lines. These spikes can
exceed 1kV! Such spikes can be high enough to cause the input fuses on the power
supply to blow and, in extreme cases, actually damage the charging circuitry. Amron
uses a medical grade power supply to isolate such faults to ensure that they will not
cause a safety issue for the diver or tender. Amron cannot guarantee that non-Amron
power supplies meet the same high standards and strongly advises against using any
such device to power your diver communicator.
4.1 BATTERY CHARGING
4.1.1 To charge the battery after use, simply connect power cord to an AC outlet rated
from 90-264 VAC, 50-60 Hz. The charger will automatically adjust to the input
voltage.
4.1.2 The unit should be placed on charge and left on charge until the unit is to be used
again. This ensures the unit will always be ready to use, and the batteries are fully
charged. The charger is designed not to damage the batteries when left on
continuous charge. Full charge will occur in ten hours (depending on the battery
age and the surrounding temperature). If the unit is in constant use (daily) it is
recommended the unit be left on charge during the weekend to top off the
batteries. Batteries must be recharged periodically, a minimum of at least once
every six months.
4.1.3 An internal 12VDC sealed lead-acid battery is supplied standard for backup
operation in the event of a loss of AC power. The switch over to battery operation is
completely automatic, and occurs whenever AC power is interrupted. The internal
12V battery is maintained at full charge while the unit is operating from AC power.
AC power indicator on the option panel confirms the presence of AC power.
4.1.4 Operating time for the 12V rechargeable battery depends on multiple factors such
as age of the battery, number of cycles, and temperature. A sealed lead-acid
battery typically has a life span of 300 cycles or 3 years, and can be charged at any
time.
NOTE: Do not continue to operate the rechargeable battery below the Low Battery Condition
or permanent damage will occur. When the battery condition indicator turns to red, turn the
unit off and charge batteries.

2820A-XX & 2825A-XX SERIES TWO DIVER COMMUNICATOR USER MANUAL
282XA-UM
REV 5.0
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4.2 BATTERY CONDITION
4.2.1 POWER ON – BATTERY CHECK
Turn power switch “ON” and observe the battery condition indicator. The battery
indicator will display the condition of the battery.
•“STEADY GREEN” light indicates the battery has sufficient voltage to operate
the unit.
•“BLINKING GREEN” light indicates the battery is low and will need charging
shortly, three hours of operating time remain.
•“STEADY RED” light indicates the battery voltage is too low to operate the unit.
Communication should stop.
NOTE: A battery, which has not been used for a period of time, will display a higher
voltage state when initially turned on, this will rapidly dissipate. This condition is
known as a surface charge, when the battery is placed under a load the voltage will
fall rapidly. It is a good idea to leave the unit on for five minutes before relying upon
the battery condition indicator.
4.3 BATTERY INSTALLATION
The 2820A-XX & 2825A-XX series communicators are supplied with a single 12V gel-cell,
sealed lead-acid battery. To remove and install the battery, remove the four brass thumb
screws from the front panel and lift unit out of the case. Set brass screws aside in a safe
place where they won’t be lost. Set unit on flat stable surface with front panel facing up.
Remove two screws on each side of the chassis. Lift out radio using the handles and set it on
its right side (side away from speaker). The 12V battery is now accessible. Lift out battery
and remove color-coded slide terminals. Install the battery and close unit in the reverse order.
4.4 MODES OF OPERATION
The 2820A and 2825A series have the ability to operate in either 2-Wire or Full Duplex (4-
Wire). Both the diver and tender can be connected in either mode and a combination of
modes can be used. If either the diver or the tender is wired in 2-Wire mode, the tender must
use a push-to-talk, either the PUSH-TO-TALK ALL SWITCH or PUSH-TO-TALK JACK, when
talking to the diver.
2-Wire communication is defined as a single communication path, normally the diver is the
priority signal path – tender listens to diver. Signal reversing is accomplished by pushing the
PUSH-TO-TALK BUTTON – diver hears tender. Often times a 4-conductor communication
cable is used with 2 wires tied together as a pair for redundancy, this is still a 2-Wire system.
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 communication. One advantage of 2-Wire is that the
tender's microphone is not active unless one of the two push-to-talk controls, PUSH-TO-
TALK BUTTON or PUSH-TO-TALK JACK, are active. This eliminates any possible acoustic
feedback between the tender's microphone and the PANEL SPEAKER. It also prevents noise
from the surface reaching the diver and allows the tender to communicate with other
members of the surface crew without involving the diver.