Amron 2820A User manual

User Manual
For
Amron International, Inc.
Model 2820A and 2825A
Two Diver Communicator
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© 2017 Amron International, Inc.

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TABLE OF CONTENTS
1INTRODUCTION AND SPECIFICATIONS ..........................................................................................1
1.1 INTRODUCTION...........................................................................................................................1
1.2 ELECTRICAL SPECIFICATIONS................................................................................................1
1.3 MECHANICAL SPECIFICATIONS...............................................................................................2
1.4 AMCOM II MODEL 2820A DIVER COMMUNICATOR................................................................3
1.5 AMCOM II MODEL 2825A DIVER COMMUNICATOR................................................................4
2LIMITED WARRANTY AND SERVICE POLICY..................................................................................5
2.1 LIMITED WARRANTY..................................................................................................................5
2.2 SERVICE POLICY........................................................................................................................5
3OPTIONS AND ACCESSORIES..........................................................................................................6
3.1 OPTIONS......................................................................................................................................6
3.2 ACCESSORIES............................................................................................................................6
4TENDER AND DIVER CONTROLS AND CONNECTIONS.................................................................8
4.1 TENDER CONTROLS ..................................................................................................................8
4.2 TENDER CONNECTIONS............................................................................................................9
4.3 DIVER CONTROLS....................................................................................................................10
4.4 DIVER CONNECTIONS..............................................................................................................10
4.5 OTHER CONNECTIONS AND CONTROLS..............................................................................11
4.6 OPTION CONTROLS: HELIUM SPEECH UNSCRAMBLER/26DSP3 .....................................12
4.7 OPTION CONTROLS: WIRELESS TENDER /28A OPTION.....................................................13
4.8 DRAWING, 2-WIRE CONNECTIONS ........................................................................................14
4.9 DRAWING, FULL DUPLEX (4-WIRE) CONNECTIONS............................................................15
4.10 DRAWING, OPERATOR CONNECTIONS, P-T-T MICROPHONE ...........................................16
5INSTALLATION AND OPERATION...................................................................................................18
5.1 OPERATION...............................................................................................................................18
5.2 CHARGING THE BATTERIES: /23 AND /24 RECHARGEABLE UNITS .................................18
5.3 BATTERY CONDITION..............................................................................................................19
5.4 BATTERY INSTALLATION –STANDARD AND /23 RECHARGEABLE UNITS.....................19
5.5 BATTERY INSTALLATION –/24 AC POWERED UNITS.........................................................19
5.6 MODES OF OPERATION...........................................................................................................20
5.7 VOLUME CONTROLS –2-WIRE...............................................................................................22
5.8 OTHER DIVER CONTROLS –(2-WIRE) ...................................................................................23
5.9 VOLUME CONTROLS –4-WIRE (FULL DUPLEX)...................................................................23
5.10 OTHER DIVER CONTROLS (4-WIRE MODE) ..........................................................................24
5.11 OTHER TENDER CONTROLS...................................................................................................24
5.12 WIRELESS OPTIONS ................................................................................................................26
6MAINTENANCE AND TROUBLESHOOTING...................................................................................28
6.1 FULL DUPLEX (4-WIRE) CHECK..............................................................................................28
6.2 2-WIRE CHECK..........................................................................................................................28
6.3 GENERAL MAINTENANCE.......................................................................................................29
6.4 RECOMMENDED MAINTENANCE SCHEDULE.......................................................................29
6.5 TROUBLESHOOTING................................................................................................................31

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7FULL DUPLEX (4-WIRE) –WHAT, WHY AND HOW .......................................................................35
7.1 WHAT ARE 2-WIRE AND 4-WIRE MODES? ............................................................................35
7.2 WHAT IS FULL DUPLEX (4-WIRE)?.........................................................................................36
7.3 WHY FULL DUPLEX (4-WIRE)?................................................................................................37
7.4 HOW DO YOU USE FULL DUPLEX (4-WIRE)?........................................................................37
8DRAWINGS ........................................................................................................................................39
8.1 PARTS IDENTIFIER FRONT PANEL MODEL 2820A ..............................................................40
8.2 PARTS IDENTIFIER, FRONT PANEL MODEL 2825A .............................................................41
8.3 PARTS IDENTIFIER, MODELS /24, /24/26DSP3 & /24/28A OPTION......................................42
9PARTS LISTS.....................................................................................................................................43
9.1 AMCOM II MODEL 2820A..........................................................................................................44
9.2 AMCOM II MODEL 2820A/23.....................................................................................................45
9.3 AMCOM II MODEL 2820A/24.....................................................................................................46
9.4 AMCOM II MODEL 2825A..........................................................................................................47
9.5 AMCOM II MODEL 2825A/23.....................................................................................................48
9.6 AMCOM II MODEL 2825A/24.....................................................................................................49
9.7 AMCOM II MODEL 2825A/24/26DSP3......................................................................................50
9.8 AMCOM II MODEL 2825A/24/26DSP3 (CONTINUED) .............................................................51
9.9 AMCOM II MODEL 2825A/24/28A.............................................................................................52
9.10 2820-301 CASE ASSEMBLY –AMCOM II................................................................................53
9.11 2820A-400M FRONT PANEL ASSEMBLY................................................................................53
9.12 2825A-400M FRONT PANEL ASSEMBLY................................................................................54
9.13 2824-500B BATTERY BOX INTERNAL CHARGER.................................................................55
9.14 28XX-FS-01 FIELD SPARES KIT FOR 2820A, 2825A .............................................................55
9.15 OPTIONAL SPARES..................................................................................................................56

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1 INTRODUCTION AND SPECIFICATIONS
1.1 INTRODUCTION
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
has independent microphone and earphone volume controls for each diver and the tender.
The Model 2820A has a single earphone volume control for diver’s volume (down-link) and a
single volume control for the tender (up-link).
AMCOM II units have push-to-talk and separate isolated inputs for each diver. Both are
portable two-diver communication systems, delivering 20 Watts “voice power”, operating from
internal batteries or external 12 VDC power source.
Models with the /24 option can be operated from either a 110/220 VAC, external 12 VDC power
source, or an internal 12 VDC battery.
The Model 2820A and Model 2825A have the capability of 2-Wire and/or Full Duplex (4-Wire)
communication modes. 2-Wire and Full Duplex (4-Wire) modes can be used simultaneously.
Full Duplex is a communications system designed from the ground-up to take advantage of
current state-of-the-art semiconductor technology and to provide superior diver hard-wire
communication.
This portable diving radio has the ability to work with both dynamic and pre-amplified
microphones in either 2-Wire or 4-Wire modes. The circuit detects the type of microphone
that each diver is using, and then automatically switches from the preamp mode to dynamic
mode, adjusting the specific diver’s gain (volume). The tender’s volume is set louder than the
diver’s volume. This allows the tender to hear the divers in a noisy environment while
maintaining the diver’s volume at a comfortable level.
1.2 ELECTRICAL 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 ............................................................................0.25 Amps
Output Impedance ........................................................................................................... 4 Ohm
Power Supply Voltage .......................................................................................12 VDC Nominal
(9 Volts Minimum - 18 Volts Maximum)
Model 282XA/24 .................................................................................... 90-264 VAC, 47-440 Hz
Sensitivity (Input) .............................................................................................................0.5 mV
Output Power (RMS @ 4 Ohm Load, 12 VDC) ..................................................20 Watts Audio

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Battery Life
Model 2820A & 2825A ................................................................................................. 40 Hours
Model 282XA/23 .......................................................................................................... 30 Hours
Model 282XA/24 .......................................................................................................... 20 Hours
1.3 MECHANICAL SPECIFICATIONS
Panel .....................................................................................Powder Coated Stainless Steel
Enclosure......................................................................................High Impact Resistant Plastic
Enclosure Color.................................................................................Bright International Yellow
Dimensions
Length ..........................................................................................................14.5 In. (36.8 Cm)
Width ............................................................................................................9.0 In. (22.9 Cm)
Height ..........................................................................................................10.0 In. (25.4 Cm)
Weight with Batteries
Model 2820A............................................................................................... 17.35 Lbs. (7.87 Kg)
Model 2820A/23 with External Charger...................................................... 20.53 Lbs. (9.31 Kg)
Model 2820A/24 ......................................................................................... 17.98 Lbs. (8.16 Kg)
Model 2825A............................................................................................... 18.20 Lbs. (8.26 Kg)
Model 2825A/23 ......................................................................................... 21.13 Lbs. (9.58 Kg)
Model 2825A/24 ......................................................................................... 18.53 Lbs. (8.40 Kg)
Model 2825A/24/26DSP3........................................................................... 19.18 Lbs. (8.70 Kg)
Model 2825A/24/28A with Remote Wireless Tender Kit .......................... 23.28 Lbs. (10.56 Kg)

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1.4 AMCOM II MODEL 2820A DIVER COMMUNICATOR
The Model 2820A AMCOM II is a full-featured, hard-wired diver communicator. The 2820A features a
single earphone volume control for the divers (downlink) and a volume control for the tender (uplink).
Divers can be wired in either 2-Wire or 4-Wire mode for maximum flexibility. It can be ordered in the
following configurations:
Non-rechargeable batteries (2820A)
Rechargeable batteries with external charger (2820A/23)
Rechargeable batteries with internal charger (2820A/24 –Shown Above)

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1.5 AMCOM II MODEL 2825A DIVER COMMUNICATOR
The Model 2825A AMCOM II is a deluxe hard-wired diver communicator. The 2825A features
individual earphone volume controls for each diver (downlink) as well as a volume control for the
tender (uplink). Both divers and the tender have microphone volume controls. Divers can be wired in
either 2-Wire or 4-Wire mode for maximum flexibility. It can be ordered in the following configurations:
Non-rechargeable batteries (2825A)
Rechargeable batteries with external charger (2825A/23)
Rechargeable batteries with internal charger (2825A/24 –Shown Above)
Rechargeable batteries with internal charger and Wireless Tender Option (2825A/24/28A)
Rechargeable batteries with internal charger and Helium Speech Unscrambler (2825A/24/
26DSP3)

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2 LIMITED WARRANTY AND SERVICE POLICY
2.1 LIMITED WARRANTY
AMRON INTERNATIONAL, INC., (Amron) warrants that its products are free from defects in
material and workmanship under normal use and service for a period of 90 days from date of
shipment as described in Amron literature covering this product. Amron’s obligation under
this warranty is limited to the repair of or replacement, at Amron’s option, of defective
material. This warranty shall not cover defects which are the result of misuse, negligence,
accident, repair or alterations.
2.2 SERVICE POLICY
For technical assistance or to request a repair, please call [phone], Monday –Friday,
8 a.m. to 5 p.m. PT. Have the model number and serial number handy and be prepared to
offer as much information as possible about the problem.
Please do not return any product without obtaining a return authorization number. Detailed
instructions will be provided at the time of request.

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3 OPTIONS AND ACCESSORIES
The following options are available to customize the AMCOM communicator. 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.
3.1 OPTIONS
3.1.1 MODEL /23 –EXTERNAL BATTERY CHARGER
The communicator is equipped with 4 gel-cell sealed lead-acid batteries and
includes an external universal input (115/230 VAC) battery charger. Operating time
is approximately 30 hours.
3.1.2 MODEL /24 –INTERNAL BATTERY CHARGER
The communicator is equipped with an internal universal input (115/230 VAC)
battery charger along with a rechargeable battery. Operating time is approximately
20 hours.
3.1.3 MODEL /26DSP3 –HELIUM SPEECH UNSCRAMBLER (HSU)
Amron’s DSP3 HSU uses state-of-the-art Digital Signal Processor (DSP)
technology to correct raw helium speech into clear, intelligible voice. The /26DSP3
option includes a complex noise reduction filter to improve communications in
situations with high background noise levels. This option must be ordered with the
/24 option and is only available on the 2825A.
3.1.4 MODEL /28A –WIRELESS TENDER OPTION
The communicator is equipped with a wireless module and includes a Model 2829-
11 Wireless Tender Headset. The wireless headset allows the tender freedom to
move around. It requires the divers to be wired in 4-Wire mode. This option must
be ordered with the /24 option and is only available on the 2825A.
3.2 ACCESSORIES
The following accessories are available for the AMCOM communicator. Accessories can be
ordered at any time.
3.2.1 MODEL 2401-28 –AMRON HEAVY-DUTY HEADSET
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 6-foot (1.8-meter) cord.
3.2.2 MODEL 2460-28 –AMRON STANDARD HEADSET
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).

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3.2.3 MODEL 2405-28 –AMRON PUSH-TO-TALK MICROPHONE
The Model 2405-28 is a hand-held, noise-canceling, push-to-talk microphone that
provides excellent sound quality to the diver. It comes equipped with a spiral cord
that can be extended up to 6 feet (1.8 meters).
3.2.4 MODEL 2822-28 –AMRON REMOTE WALK-AND-TALK MODULE
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.
3.2.5 MODEL 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.
3.2.6 MODEL 2829-11 –AMRON WIRELESS TENDER HEADSET
A heavy-duty headset combined with a wireless belt module that is compatible with
the /28A option. One headset comes with communicators ordered with the /28A
options but additional headset can be ordered to allow other crew member to
monitor communications.

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4 TENDER AND DIVER 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. We strongly recommend the tender read FULL
DUPLEX (4-WIRE) –WHAT, WHY AND HOW located in section 7 of this manual.
4.1 TENDER 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 ALL DIVERS BUTTON –This button 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. When using Full Duplex mode, this
control allows the tender to interrupt the divers by forcing them into listen only
mode.
4.1.4 EARPHONE VOLUME –This control sets the volume for the tender's earphone
and/or PANEL SPEAKER. Rotate this knob clockwise to increase the volume from
all the divers.
4.1.5 MICROPHONE VOLUME (Model 2825A only) –This control sets the level for the
tender's microphone and/or PANEL MICROPHONE. Rotate this knob clockwise to
increase the tender’s volume to all the divers.
4.1.6 BATTERY CONDITION INDICATOR –A steady GREEN light indicates battery
charge level is good. Blinking GREEN light indicates battery charge level is at a low
level with less than 3 hours of running time available. Steady RED light indicates
battery charge level is below the level necessary to guarantee proper operation.
WARNING: When BATTERY CONDITION INDICATOR is steady RED light, the
batteries should be replaced or recharged immediately.
4.1.7 PANEL SPEAKER –A waterproof, acoustic horn speaker that allows the tender to
listen to the divers. The volume level is controlled by the EARPHONE VOLUME
control and it can be turned off using the SPEAKER SWITCH.
4.1.8 PANEL MICROPHONE –A water-resistant condenser microphone that allows the
tender to talk to the divers using the PUSH-TO-TALK BUTTONS. On the 2825A,
the volume level is controlled by the MICROPHONE VOLUME control. The PANEL
MICROPHONE is muted when the SPEAKER SWITCH is turned off.
WARNING: Do not plug or cover the PANEL MICROPHONE hole. This may
dampen the tender-to-diver communications or damage the microphone
requiring replacement.

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4.2 TENDER CONNECTIONS
4.2.1 TENDER HEADSET JACK –This is the dual banana jack (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 the wiring diagram in section 4.9.
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).
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 the wiring
diagram in section 4.8. 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 the wiring diagram in section 4.10. 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.

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4.2.2 TENDER MICROPHONE JACK –This is a dual banana jack (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. On the 2825A, the TENDER
MICROPHONE VOLUME control adjusts the sensitivity of the input.
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. 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.
4.3 DIVER CONTROLS
4.3.1 DIVER EARPHONE VOLUME (Model 2820A) –This control sets the earphone
volume level to both divers.
4.3.2 DIVER EARPHONE VOLUME (Model 2825A) –The 2825A has separate earphone
volume controls for each diver. This allows the tender to set the best individual
volume for each diver.
4.3.3 DIVER MICROPHONE (Model 2825A) –The 2825A has separate microphone
volume controls for each diver. This sets amplification level of each diver’s
microphone signal controlling that diver’s volume to both the tender and the other
diver.
4.3.4 PUSH-TO-TALK-DIVER –There is a separate PUSH-TO-TALK button for each
diver. Normally used in 2-Wire mode, this control allows the tender to talk to only
one of the divers. The diver selected will hear both the tender and the other diver
allowing crosstalk between the divers controlled by the tender. It can be used in
Full Duplex (4-Wire) to cut off the microphone of an individual diver.
4.4 DIVER CONNECTIONS
4.4.1 DIVER MICROPHONE –This 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
regardless of the mode used for the diver.
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 wiring diagram in section 4.8. 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

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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 as shown in the
wiring diagram in section 4.9. The diver can use this mode even if the tender is
wired in 2-Wire mode.
4.4.2 DIVER EARPHONE –This 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.
4.5 OTHER CONNECTIONS AND CONTROLS
4.5.1 EXTERNAL BATTERY JACK –The communicator can be powered using an
external battery or power supply via the two 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 18 VDC and must be able to supply a peak current
of 3 Amps for proper operation. The following warnings need to be heeded when
using the EXTERNAL BATTERY JACK. A minimum wire size of 18 AWG and
maximum wire run of 3 feet (1 meter) is recommended.
It is strongly recommended that an Amron External Charger Model 2823-603 be
used as the external power supply. The Amron External Charger was specifically
designed for use with all Amron communicators and has a high degree of insulation
between the primary and secondary circuits for diver protection and safety.
WARNING: The EXTERNAL BATTERY JACK can be used to recharge the
2820A/23 & 2825A/23 with rechargeable sealed lead acid battery. It is strongly
advised to use the provided Amron External Charger, Model 2823-603, to
charge or operate the communicator. This charger has been designed with
the necessary electrical isolation to prevent dangerous currents from the AC
lines from reaching the diver.
If you use an external power supply, the maximum voltage needs to be
limited to 15 Volts if the rechargeable battery is in the unit. If a higher voltage
is to be used, it is advised that the battery be disconnected or removed from
the communicator to prevent possible damage to the battery.
4.5.2 TAPE RECORDER –This 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.
4.5.3 AC POWER (/24 Option) –The AC power cord is located in the option panel
located on right side of the communicator front panel. The option panel has an AC
POWER LED to identify the presence of AC power. When the communicator is
plugged into AC power, the LED will be on regardless of the POWER SWITCH.
The internal battery charger has a universal input voltage range from 90-264
VRMS over a frequency range from 47-440Hz. No operator adjustment is required.

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4.6 OPTION CONTROLS: HELIUM SPEECH UNSCRAMBLER/26DSP3
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.
4.6.1 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.
4.6.2 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.

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4.6.3 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.
4.6.4 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 17 dB.
4.7 OPTION CONTROLS: WIRELESS TENDER /28A OPTION
This option is mounted in the right hand side of the front panel. This Wireless Tender Option
is for four-wire (Full Duplex) operation only. System comes standard with a remote wireless
tender module.
4.7.1 WIRELESS OPTION PANEL –Comes standard with antenna and power on/off
switch. The “ON/OFF” switch powers the wireless PC card inside the
communicator. The antenna has a swivel and tilt that allows the antenna to be
folded down during shipment. For operation, the antenna should be pointing
upwards. For installations where the Diver Communicator is located inside a
structure, there is an optional Remote Antenna kit available. This kit allows the
antenna to be located outside the structure for maximum effective range.
IMPORTANT: When the wireless option is not used, turn the option panel switch to
“OFF”. When option panel switch is turned “ON”, the wireless remote should be
“ON”. Otherwise a static noise may be heard through the communicator’s panel
speaker as it scans for available Remote Wireless Tender.
4.7.2 REMOTE WIRELESS TENDER MODULE –This module comes standard with an
internal rechargeable battery. Headset and external 110V charger jacks are located
on remote module.
4.7.3 ON/OFF-VOLUME CONTROL –Adjusts the listening volume and turns the unit
“OFF” when it is turned completely upwards.
4.7.4 TALK PUSH BUTTON –This button is located on the top of the unit and is labeled
TALK. When it’s first turned on, the Remote Wireless Tender Module is in Standby
Mode (listen only) as indicated by the LED closest to the button being red. When
the button is pressed, the Remote Wireless Tender Module is in “Talk Mode” (listen
and talk, full duplex) and the LED is green. Pressing the TALK button toggles
between the two modes. Multiple Remote Wireless Tender Modules can be in the
Standby (listen only) mode at the same time. Only one module can be in the talk
mode.
4.7.5 HEADSET JACK –Located on the side opposite the ON/OFF-Volume Control.
Plug the remote wireless headset to this jack.
4.7.6 CHARGE JACK –Located on the side next to the ON/OFF-Volume Control. Plug
the remote wireless charger to this jack.

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4.8 DRAWING, 2-WIRE CONNECTIONS

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4.9 DRAWING, FULL DUPLEX (4-WIRE) CONNECTIONS

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4.10 DRAWING, OPERATOR CONNECTIONS, P-T-T MICROPHONE
DRAWING, OPERATOR CONNECTIONS, HEADSET