Garmin GMA 347 User manual

£
Garmin Ltd. or its subsidiaries
190-00325-01 Revision A
August 2005
GMA 347
A
UDIO PANEL
INSTALLATION
MANUAL

Page A GMA 347 Installation Manual
Revision A 190-00325-01
© Copyright 2005
Garmin Ltd. or its subsidiaries
All Rights Reserved
Except as expressly provided herein, no part of this manual may be reproduced, copied, transmitted, disseminated,
downloaded or stored in any storage medium, for any purpose without the express prior written consent of Garmin.
Garmin hereby grants permission to download a single copy of this manual and of any revision to this manual onto a
hard drive or other electronic storage medium to be viewed and to print one copy of this manual or of any revision
hereto, provided that such electronic or printed copy of this manual or revision must contain the complete text of
this copyright notice and provided further that any unauthorized commercial distribution of this manual or any
revision hereto is strictly prohibited.
Garmin International, Inc.
1200 E. 151st Street
Olathe, KS 66062 USA
Telephone: [phone]
www.garmin.com
Garmin (Europe) Ltd.
Unit 5, The Quadrangle, Abbey Park Industrial Estate
Romsey, SO51 9DL, U.K.
Telephone: [phone]
RECORD OF REVISIONS
Revision Revision
Date
Description ECO #
A8/24/05 Initial Release 33101
DOCUMENT PAGINATION
Section Page Range
Table of Contents i-viii
Section 1 1-1 – 1-6
Section 2 2-1 – 2-8
Section 3 3-1 – 3-14
Section 4 4-1 – 4-14
Section 5 5-1 – 5-10
Appendix A A-1-A-6
Appendix B B-1-B-6
Appendix C C-1-C-24

GMA 347 Installation Manual Page i
190-00325-01 Revision A
At the time of this edition, the current software version for the GMA 347 is 2.09.
The software version and information in this document are subject to change without
notice. Visit the Garmin web site (www.garmin.com) for current manual updates and
supplemental information concerning the operation of this and other Garmin
products.
INFORMATION SUBJECT TO EXPORT CONTROL LAWS
This document may contain information which is subject to the Export Administration Regulations
("EAR") issued by the United States Department of Commerce (15 CFR, Chapter VII, Subchapter C) and
which may not be exported, released, or disclosed to foreign nationals inside or outside of the United
States without first obtaining an export license. A violation of the EAR may be subject to a penalty of up
to 10 years imprisonment and a fine of up to US $1,000,000 under Section 2410 of the Export
Administration Act of 1979. Include this notice with any reproduced portion of this document.
WARNING
This product, its packaging, and its components contain chemicals known to the state of California to
cause cancer, birth defects, or reproductive harm. This notice is being provided in accordance with
California’s proposition 65. If you have any questions or would like additional information, please refer
to our web site at www.garmin.com/prop65.
NOTE

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GMA 347 Installation Manual Page iii
190-00325-01 Revision A
TABLE OF CONTENTS
PARAGRAPH PAGE
1 GENERAL DESCRIPTION..............................................................................................................1-1
1.1 Introduction........................................................................................................................................1-1
1.2 Equipment Description ......................................................................................................................1-1
1.3 Technical Specifications ...................................................................................................................1-3
1.4 Certification .......................................................................................................................................1-5
1.5 Reference Documents ........................................................................................................................1-6
1.6 Limited Warranty...............................................................................................................................1-6
2 INSTALLATION OVERVIEW ........................................................................................................2-1
2.1 Introduction........................................................................................................................................2-1
2.2 Wiring................................................................................................................................................2-1
2.3 Cooling Air ........................................................................................................................................2-1
2.4 Installation Materials .........................................................................................................................2-2
2.5 GMA 347 Wiring and Software Configuration Options....................................................................2-3
2.6 Marker Beacon Antenna Installation .................................................................................................2-5
2.7 Installation Approval Considerations for Pressurized Aircraft..........................................................2-6
2.8 Electrical Noise..................................................................................................................................2-6
2.9 GMA 347 Mounting ..........................................................................................................................2-7
3 INSTALLATION PROCEDURE......................................................................................................3-1
3.1 Unpacking Unit..................................................................................................................................3-1
3.2 Marker Beacon Antenna Installation .................................................................................................3-1
3.3 Marker Beacon Antenna Cable Connectors.......................................................................................3-1
3.4 Electrical Connections .......................................................................................................................3-1
3.5 Backshell Assembly and D-Subminiature Connectors ......................................................................3-3
3.6 Circuit Breaker Placard....................................................................................................................3-11
3.7 GMA 347 Unit Installation..............................................................................................................3-11
3.8 Post Installation Configuration and Checkout .................................................................................3-11
4 SYSTEM INTERCONNECTS..........................................................................................................4-1
4.1 Connector Description .......................................................................................................................4-1
4.2 Connectors J3471 and J3472 .............................................................................................................4-1
4.3 J3472 Connector Pin Assignments ....................................................................................................4-6
4.4 J3471 Connector Pin Assignments ..................................................................................................4-10

Page iv GMA 347 Installation Manual
Revision A 190-00325-01
TABLE OF CONTENTS
PARAGRAPH PAGE
5 POST INSTALLATION CONFIGURATION AND CHECKOUT PROCEDURE .........................5-1
5.1 Post Installation Configuration Harness ............................................................................................5-1
5.2 Program Information..........................................................................................................................5-1
5.3 GMA Configuration Tool Version ....................................................................................................5-1
5.4 GMA Configuration Tool Introduction .............................................................................................5-1
5.5 Connect and Disconnect Buttons.......................................................................................................5-2
5.6 Configuration Tool Settings ..............................................................................................................5-4
5.7 Marker Beacon...................................................................................................................................5-5
5.8 Keypad Annunciators ........................................................................................................................5-5
5.9 Configuration Inputs..........................................................................................................................5-5
5.10 Code Upload ......................................................................................................................................5-6
5.11 Configuration Example......................................................................................................................5-9
5.12 Valid Data Ranges ...........................................................................................................................5-10
APPENDIX A CERTIFICATION DOCUMENTS
A.1 Airworthiness Approval....................................................................................................................A-1
A.2 Continued Airworthiness ..................................................................................................................A-1
A.3 Environmental Qualification Forms, GMA 347 Audio Panel .......................................................... A-3
APPENDIX B ASSEMBLY AND INSTALLATION DRAWINGS
APPENDIX C INTERCONNECT DRAWINGS
LIST OF ILLUSTRATIONS
FIGURE PAGE
2-1 GMA 347 Unit Rack .........................................................................................................................2-7
3-1 Shield Block Install onto Backshell Connector Assembly ................................................................3-4
3-2 Shielded Cable Preparation................................................................................................................3-5
3-3 Daisy Chain Method for Shield Termination.....................................................................................3-8
3-4 Parallel Shield Termination ...............................................................................................................3-8
3-5 Configuration Module Installation...................................................................................................3-10
4-1 Back of Unit, Connector Location.....................................................................................................4-1
4-2 Rear Connectors J3471 and J3472, Viewed From Back of Unit .......................................................4-1
4-3 GMA 347 Configuration Upload Connections..................................................................................4-7

GMA 347 Installation Manual Page v
190-00325-01 Revision A
LIST OF ILLUSTRATIONS
FIGURE PAGE
5-1 About GMA Config Tool ..................................................................................................................5-1
5-2 GMA Configuration Tool Screen ......................................................................................................5-2
5-3 Connecting to the GMA 347..............................................................................................................5-2
5-4 Radio Button Not Chosen and Upload Selected................................................................................5-6
5-5 File Selection .....................................................................................................................................5-6
5-6 Wrong Hex File Selected (Selecting Boot Code for System Code Upload)......................................5-6
5-7 Wrong Hex File Selected (Selecting System Code for System Code Upload)..................................5-7
5-8 Erasing Flash .....................................................................................................................................5-7
5-9 Uploading Flash.................................................................................................................................5-7
5-10 Canceling a Code Upload ..................................................................................................................5-7
5-11 Code Upload Failed ...........................................................................................................................5-8
5-12 Code Upload Complete......................................................................................................................5-8
A-1 GMA 347 Environmental Qualification Form .................................................................................A-4
B-1 GMA 347 Outline Drawing .............................................................................................................. B-1
B-2 GMA 347 Rack Dimensions (115-00427-00)................................................................................... B-3
B-3 GMA 347 Connector/Rack Assembly Drawing .............................................................................. B-5
C-1 GMA 347 Power, Antenna and Speaker Interconnect Wiring Diagram........................................... C-1
C-2 Mic and Phone Jack Connections, Interconnect Wiring Diagram.................................................... C-3
C-3 Transceiver Analog Connections, Interconnect Wiring Diagram..................................................... C-5
C-4 Discrete Lines, Interconnect Wiring Diagram ..................................................................................C-7
C-5 GMA 340 to GMA 347 Comparison ................................................................................................C-9

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Revision A 190-00325-01
LIST OF TABLES
TABLE PAGE
3-1 Pin Contact Part Numbers..................................................................................................................3-1
3-2 Recommended Crimp Tools ..............................................................................................................3-2
3-3 Backshell Assembly...........................................................................................................................3-3
3-4 Shield Block Components .................................................................................................................3-4
3-5 Shielded Cable Preparation................................................................................................................3-5
3-6 Configuration Module Kit – 011-00979-00.......................................................................................3-9
3-7 Configuration Module Wire Color Reference Chart .......................................................................3-10
4-1 J3471 Pin Assignments......................................................................................................................4-2
4-2 J3472 Pin Assignments......................................................................................................................4-4
4-3 Aircraft Power Pin Assignments, J3472 ............................................................................................4-6
4-4 Aircraft Lighting Pin Assignments, J3472.........................................................................................4-6
4-5 RS-232 Pin Assignments, J3472........................................................................................................4-7
4-6 Marker Beacon Pin Assignments, J3472 ...........................................................................................4-8
4-7 Installation Selection Inputs Pin Assignments, J3472 .......................................................................4-8
4-8 External Configuration Module Pin Assignments, J3472..................................................................4-9
4-9 Speaker Pin Assignments, J3472 .......................................................................................................4-9
4-10 PA MUTE Pin Assignments, J3472 ..................................................................................................4-9
4-11 Mic Audio Inputs and Mic Key Pin Assignments, J3471................................................................4-10
4-12 ICS Key Pin Assignments, J3471 ....................................................................................................4-10
4-13 Com Audio and Mic Keys Pin Assignments, J3471........................................................................4-11
4-14 Nav Audio Pin Assignments, J3471 ................................................................................................4-11
4-15 Headset Outputs Pin Assignments, J3471 .......................................................................................4-11
4-16 Music Inputs Pin Assignments, J3471.............................................................................................4-12
4-17 Unswitched Audio Inputs Pin Assignments, J3471.........................................................................4-12
4-18 Telephone Inputs/Outputs Pin Assignments, J3471 ........................................................................4-12
4-19 AUX, DME and ADF Audio Pin Assignments, J3471....................................................................4-13
4-20 Failsafe Audio Pin Assignments, J3471 ..........................................................................................4-13

GMA 347 Installation Manual Page vii
190-00325-01 Revision A
GMA 347 HARDWARE MOD LEVEL HISTORY
The following table identifies hardware modification (Mod) Levels for the GMA 347 Audio Panel. Mod
Levels are listed with the associated service bulletin number, service bulletin date, and the purpose of the
modification. The table is current at the time of publication of this manual (see date on front cover) and is
subject to change without notice. Authorized Garmin Sales and Service Centers are encouraged to access
the most up-to-date bulletin and advisory information on the Garmin Dealer Resource web site at
www.garmin.com using their Garmin-provided user name and password.
MOD
LEVEL
SERVICE
BULLETIN
NUMBER
SERVICE
BULLETIN
DATE
PURPOSE OF MODIFICATION

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GMA 347 Installation Manual Page 1-1
190-00325-01 Revision A
1 GENERAL DESCRIPTION
1.1 Introduction
This manual presents mechanical and electrical installation requirements for installing the Garmin
GMA 347 Audio Panel. The GMA 347 can be installed into a variety of airframes by means of an STC,
TC or Field Approval. Each airframe installation may vary. Use only approved data for specific
installation instructions in a particular aircraft. After installation of the GMA 347, FAA Form 337 must
be completed by an appropriately certificated agency to return the aircraft to service.
1.2 Equipment Description
CAUTION
The operation of cellular telephones or other cellular mobile devices aboard aircraft while
airborne is prohibited by FCC rules. Due to the potential for interference with onboard
systems, the operation of cellular communication devices while onboard an aircraft that is
on the ground is subject to (FAA) 14 CFR 91.21.
(FCC) 47 CFR 22.925 prohibits airborne operation of cellular telephones installed in or
carried aboard aircraft. Cellular telephones must not be operated aboard any aircraft
while the aircraft is off the ground. When any aircraft leaves the ground, all cellular
telephones on board that aircraft must be turned off.
Cellular telephones that are on, even in a monitoring state, can disrupt GPS performance.
The Garmin GMA 347 is a horizontally oriented panel-mounted audio control panel and marker beacon
system. The system delivers reliability and versatility for all audio controlling functions. LED-
illuminated pushbuttons and logical panel layout allow audio selection of NAV, COM. LED annunciator
brightness is adjusted to an appropriate level for ambient cockpit light conditions automatically by
photocell dimming. Key brightness is controlled manually with the radio lighting dimming bus. A
failsafe circuit connects the pilot’s left headset channel and microphone directly to COM 1 in case power
is interrupted or the unit is turned off.
The Garmin GMA 347 Audio Panel incorporates a microcontroller for processing front panel key
commands, annunciator control, input/output functions, and communication.
The GMA 347 includes a six-position intercom system (ICS) with electronic cabin noise de-emphasis,
two stereo music inputs, and combined pilot, copilot, and passenger volume controls. The intercom
provides four selectable modes of isolation (All, Crew, Pilot, Copilot). A pilot-selectable cabin speaker
output can be used to listen to the selected aircraft radios or to broadcast PA announcements. The PA
function is pilot selectable.
The GMA 347 provides a digital voice recorder with playback capability. Recording is automatic when a
COM signal is received. Playback is controlled by pressing the PLAY button or a remote mounted
switch.

Page 1-2 GMA 347 Installation Manual
Revision A 190-00325-01
The Recorder can be disabled using an external switch. The digital recorder can playback up to two and a
half minutes of recording. Refer to the GMA 347 Pilot’s Guide (190-00325-00) for complete system
operation.
The GMA 347 is FAA TSO approved to C50c and C35d Class A, and ETSO approved to C50c and
2C35d (pending). A marker beacon receiver with dual sensitivity and audio muting with automatic re-
arming is included in the unit. Operating voltage range is from 11 to 33 volts.
The GMA 347 provides two stereo auxiliary entertainment inputs; MUSIC 1 and MUSIC 2. Two 3.5 mm
stereo phone jacks should be installed in a convenient location for this purpose. These inputs are
compatible with popular portable entertainment devices such as MP3 and CD players. The headphone
outputs of these devices are plugged into the MUSIC 1 or MUSIC 2 jacks.
Only the pilot and copilot hear MUSIC 1. MUSIC 2 is a non-muted input heard only by the passengers.
MUSIC 1 and MUSIC 2 characteristics are affected by the active intercom mode. Refer to the GMA 347
pilot’s manual for details.
MUSIC 1 is soft-muted when an interruption occurs from an aircraft radio. Soft muting is the gradual
return of MUSIC 1 to its original volume level. MUSIC 1 can also be configured to mute during ICS
activity. MUSIC 2 is a non-muted input.
1.2.1 Features Summary
•Logical front panel layout
•LED annunciators indicate selected function
•Six position intercom: pilot, copilot, four passengers
•Three stereo headset amplifiers: one for pilot, one for copilot, and one for the passengers
•Two stereo music source inputs
•Four selectable intercom operational modes
•Independent pilot, copilot, and passenger volume control
•VOX control for mic inputs
•Automatic selection of radio audio source when corresponding mic is selected
•MASQTM Processing
•Split COM transceiver function. Copilot may transmit and receive on COM 2 while pilot
transmits and receives on COM 1
•COM swap function
•TX indication
•SmartMuteTM marker audio muting
•Autosquelch
•Speaker output for radios or PA function
•Power-off fail safe connection for Pilot PTT, mic and Pilot’s Headset-Left to COM 1
•Voice Recorder with Playback
•Configurable Options. See Sections 4 and 5 for connection and configuration details.

GMA 347 Installation Manual Page 1-3
190-00325-01 Revision A
1.2.2 Interface Summary
The following is an interface summary for the GMA 347. See Section 4 and Appendix C for connection
details.
•3 Transceiver Inputs (Figure C-3)
•5 Receiver Inputs (Figure C-3)
•4 Unswitched Inputs (Figures C-3)
•2 Aircraft Power Inputs (Figure C-1)
•Discrete Inputs/Outputs (Figure C-4)
•Marker Beacon Antenna Input (Figure C-1)
•External Marker Beacon Lamp Driver Outputs (Figure C-4)
1.3 Technical Specifications
The following tables present general environmental specifications. For detailed specifications, see the
Environmental Qualification form in Appendix A.
1.3.1 Physical Characteristics
Specification Characteristic
Bezel Height 1.3 inches (33 mm)
Bezel Width 6.29 inches (160 mm)
Rack Height 1.325 (34 mm)
Rack Width 6.30 inches (160 mm)
Depth Behind Panel with
Connectors (measured from face
of aircraft panel to rear of
connector backshells)
7.79 inches (198 mm)
GMA 347 Unit Weight 1.7 lbs. (0.8 kg)
GMA 347 Rack Weight (Installed
with rack and connectors)
2. 4 lbs. (1.1 kg)

Page 1-4 GMA 347 Installation Manual
Revision A 190-00325-01
1.3.2 Electrical Characteristics
Specification Characteristic
Regulatory Compliance RTCA/DO-160D Environmental Conditions and EUROCAE/ED-14D
Unit Software RTCA/DO-178B Level D
Temperature Range -45°C to +70°C
Altitude 55,000 Feet
Audio Panel Transceiver inputs: 3
Receiver inputs: 5
Unswitched inputs: 4
Input impedance: 500 
Input isolation: 60 dB minimum
Special functions: Failsafe operation, MASQTM
processing
Maximum Input: COM, NAV, DME, AUX, Failsafe, Unswitched inputs 1-3,
Altitude Warning; 4 V rms
TEL; 3.5 V rms
Intercom Positions: 6 (pilot, copilot, 4 passengers)
Volume controls: 2 (pilot, copilot/passengers)
VOX level controls: 2 (pilot, copilot/passengers)
VOX circuits: 6 (one per mic input)
Music inputs (stereo): 2 (one input mutable)
Music input impedance: 5 k
Music input level: Less than 500 mVac RMS for full output (typical).
1 Vac RMS MAX (3 Vac p-p)
Microphone signal processing: 9 pole characteristic and special cabin
noise band de-emphasis
Intercom isolation modes: 4 (All, Pilot Isolate, Copilot Isolate, Crew
Isolate)
Special functions: Recorder with playback (automatic recording of
selected COMs) up to 2.5 minutes of recording time.
Automatic squelch: 6 (one per mic input) pilot selectable between auto
and manual.
Headphone Outputs Output amplifiers: 3, stereo (pilot, copilot, passengers)
Fidelity: Power into 150 Distortion
50 mW <0.5%
100 mW <5%
Frequency response: music; 50 Hz to 20 kHz nominal
Aircraft radio: 200 Hz to 6 kHz nominal
ICS mic: (Special cabin noise band de-emphasis)
Speaker Outputs Outputs selectable: 1, pilot selectable
Output power: 10 watts into 4 or 8 , @ any normal supply voltage.
Frequency response: 350 Hz to 6 kHz nominal
Special functions: PA Mode, pilot selectable, including split operation
Marker Beacon Receiver Frequency: Crystal controlled at 75 MHz
Sensitivity: LO 1000 µV hard; HI 200 µV hard
Selectivity: 6 dB @ ±10 kHz min, 40 dB @ ±200 kHz max.
Input impedance: 50 
External lamp drive: 125 mA max each output
Other outputs: Middle MKR sense
Special functions:SmartMuteTM marker audio muting

GMA 347 Installation Manual Page 1-5
190-00325-01 Revision A
1.3.3 Power Requirements
Characteristic Specification
Input Voltage Range 11.0 to 33.0 Vdc. See the Environmental Qualification
Form in Appendix A for details on surge ratings and
minimum/maximum operating voltages.
Power Input Operating Current:
3.75 amps max at 13.75 V
1.75 amps max at 27.5 V
1.4 Certification
The conditions and tests required for TSO approval of this article are minimum performance standards. It
is the responsibility of those installing this article either on or within a specific type or class of aircraft to
determine that the aircraft installation conditions are within the TSO standards. TSO articles must have
separate approval for installation in an aircraft. The article may be installed only if performed under 14
CFR part 43 or the applicable airworthiness requirements.
1.4.1 TSO/ETSO Compliance
The GMA 347 is FAA TSO approved to TSO-C50c, TSO-C35d Class A, ETSO-C50c (pending) and
ETSO-2C35d (pending).
For a list of ETSO deviations see the GMA 347 Declaration of Design and Performance, Garmin part
number 190-00325-03.
1.4.2 TSO Deviations
The following table provides a list of applicable TSO deviations for the GMA 347.
TSO Deviation
Garmin was granted a deviation from TSO-C35d to use RTCA DO-160D instead of RTCA
DO-138 as the standard for Environmental Conditions and Test Procedures for Airborne
Equipment.
TSO-C35d
Garmin was granted a deviation from TSO-C35d to use FAR §21.607(d) instead of FAR
§37.7 as the general rules governing holders of the TSO authorizations.
Garmin was granted a deviation from TSO-C50d to use RTCA DO-178B instead of RTCA
DO-178A as the standard for Software Considerations in Airborne Systems and
Equipment Certification.
TSO-C50d
Garmin was granted a deviation from TSO-C50d to use RTCA DO-160D instead of RTCA
DO-160A as the standard for Environmental Conditions and Test Procedures for Airborne
Equipment.

Page 1-6 GMA 347 Installation Manual
Revision A 190-00325-01
1.5 Reference Documents
The following publications are sources of additional information for installing the GMA 347. Before
installing the unit, the technician should read all referenced materials along with this manual.
Part Number Document
190-00325-00 GMA 347 Pilot’s Guide
1.6 Limited Warranty
This Garmin product is warranted to be free from defects in materials or workmanship for two years from
the date of purchase. Within this period, Garmin will at its sole option, repair or replace any components
that fail in normal use. Such repairs or replacement will be made at no charge to the customer for parts or
labor, provided that the customer shall be responsible for any transportation cost. This warranty does not
cover failures due to abuse, misuse, accident or unauthorized alteration or repairs.
THE WARRANTIES AND REMEDIES CONTAINED HEREIN ARE EXCLUSIVE AND IN LIEU OF
ALL OTHER WARRANTIES EXPRESS OR IMPLIED OR STATUTORY, INCLUDING ANY
LIABILITY ARISING UNDER ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE, STATUTORY OR OTHERWISE. THIS WARRANTY GIVES YOU
SPECIFIC LEGAL RIGHTS, WHICH MAY VARY FROM STATE TO STATE.
IN NO EVENT SHALL GARMIN BE LIABLE FOR ANY INCIDENTAL, SPECIAL, INDIRECT OR
CONSEQUENTIAL DAMAGES, WHETHER RESULTING FROM THE USE, MISUSE, OR
INABILITY TO USE THIS PRODUCT OR FROM DEFECTS IN THE PRODUCT. Some states do not
allow the exclusion of incidental or consequential damages, so the above limitations may not apply to
you.
Garmin retains the exclusive right to repair or replace the unit or software or offer a full refund of the
purchase price at its sole discretion. SUCH REMEDY SHALL BE YOUR SOLE AND EXCLUSIVE
REMEDY FOR ANY BREACH OF WARRANTY.
To obtain warranty service, contact your local Garmin Authorized Service Center. For assistance in
locating a Service Center near you, call Garmin Customer Service at one of the numbers shown below.
Products sold through online auctions are not eligible for rebates or other special offers from Garmin.
Online auction confirmations are not accepted for warranty verification. To obtain warranty service, an
original or copy of the sales receipt from the original retailer is required. Garmin will not replace missing
components from any package purchased through an online auction.
Garmin International, Inc. Garmin (Europe) Ltd.
1200 East 151st Street Unit 5, The Quadrangle, Abbey Park Industrial Estate
Olathe, Kansas 66062, U.S.A. Romsey, SO51 9DL, U.K.
Phone: [phone] Phone: [phone]
FAX: [phone] FAX: [phone]

GMA 347 Installation Manual Page 2-1
190-00325-01 Revision A
2 INSTALLATION OVERVIEW
2.1 Introduction
This section provides hardware equipment information for installing the GMA 347 Audio Panel, related
hardware and suggestions relating to the marker beacon antenna. Installation of the GMA 347 should
meet the requirements of FAA Advisory Circulars AC 43.13-1B and AC 43.13-2A where applicable.
Cabling is fabricated by the installing agency to fit each particular aircraft.
2.2 Wiring
Use AWG #22 or larger wire for all connections unless otherwise specified in the interconnect diagrams
in Appendix C. The standard pin contacts supplied in the connector kit are compatible with up to AWG
#22 wire. In cases where some installations have more than one unit sharing a common circuit breaker,
sizing and wire gauge is based on aircraft circuit breaker layout, length of wiring, current draw of units,
and internal unit protection characteristics. Do not attempt to combine more than one unit on the same
circuit breaker unless it is specified on aircraft manufacturer approved drawings.
In some cases, a larger gauge wire such as AWG #18 or #16 may be needed for power connections.
Extended barrel contacts for AWG #16 and #18 wire are available from Garmin, if required. Special
thin-wall heat shrink tubing is also provided to insulate the extended barrels inside the backshell. If using
#16 or #18 barrel contacts, ensure that no two contacts are mounted directly adjacent to each other. This
minimizes the risk of contacts touching and shorting to adjacent pins and to ground.
Ensure that routing of the wiring does not come in contact with sources of heat, RF or EMI interference.
Check that there is ample space for the cabling and mating connectors. Avoid sharp bends in cabling and
routing near aircraft control cables.
2.3 Cooling Air
The GMA 347 does not have provisions for attaching cooling air and does not generate an excessive
amount of heat during typical operations, however the thermal characteristics of the installation should
always be assessed. An undesireable thermal condition could be created due to the unit's own internal
power dissipation combined with restricted ventilation, or due to heat generated by adjacent equipment.
Limiting thermal build up, by means of fan or natural convection is always a good practice and is
recommended to increase the product life.

Page 2-2 GMA 347 Installation Manual
Revision A 190-00325-01
2.4 Installation Materials
2.4.1 Configurations Available
The GMA 347 is available in three versions under the following part numbers. Catalog part numbers are
shown with and without the installation kit.
Model Front Panel
Color
Unit P/N Catalog P/N Installation
Kit
GMA 347 Black 011-00807-00 010-00275-00 No
GMA 347 Black 011-00807-00 010-00275-01 Yes
GMA 347 Gray 011-00807-10 010-00275-10 No
GMA 347 Gray 011-00807-10 010-00275-11 Yes
GMA 347H Black 011-00807-20 010-00275-20 No
GMA 347H Black 011-00807-20 010-00275-21 Yes
2.4.2 Equipment Available
Each of the following accessories is provided separately or in kit form for the GMA 347. The installation
kit includes the unit and the following hardware:
Item Garmin P/N
Sub Assy, Connector Kit, GMA 347 011-00813-01
SMP, Install Rack, GMA 347 115-00427-00
Sub Assy, Backplate, GMA 347 011-00812-00
Configuration Module Kit 011-00979-00
Garmin Marker Beacon Antenna Kit** 010-10175-00
** Note: A marker beacon antenna approved to TSO C35d that has been installed to meet the
requirements of this manual may be approved for use with the GMA 347.
2.4.3 Additional Equipment Required
•Antenna sealant (use manufacturer’s instructions, install according to FAA Advisory Circular
AC 43.13-2A).
•Cables: The installer will fabricate and supply all system cables. Interconnect wiring
diagrams are detailed in Appendix C.
•Hardware #6-32 x 100° Flat Head SS Screw [(MS24693, AN507R or other approved
fastener) (6 ea.)] and #6-32 Self-Locking Nut [MS21042 or other approved fastener (6 ea.)].
Hardware required to mount the installation rack is not provided.
•Stereo headphone jacks (up to 6), microphone jacks (up to 6), 3.5 mm stereo jacks (up to 2),
and insulating washers for all.

GMA 347 Installation Manual Page 2-3
190-00325-01 Revision A
2.5 GMA 347 Wiring and Software Configuration Options
The GMA 347 can be configured in different ways for the flight crew. Consideration of options should
be discussed with the end user(s) of the aircraft before wiring begins. While Section 4 and Appendix C
contain connection details, the actual features employed or omitted are dependent on the wiring options
and the Software configuration selected. Refer to Section 5 for configuration instructions.
2.5.1 Hard Wiring Configuration Options
The following list shows the hard wiring configuration options available for the GMA 347.
Function and Purpose Hard Wiring Configuration Options
Com Swap. Transfers the active
microphone between Com 1 and
Com 2.
Com Swap Pushbutton Switch
External lamps. Provides an extra
set of Marker Beacon indicators
located away from the GMA 347.
External Marker Beacon Lights
Two Playback Options:
An external pushbutton activates
voice recorder playback.
A toggle switch enables or
disables recording.
Record Playback Pushbutton Switch
Record Playback Toggle Switch
PA MUTE is an output from the
GMA that is pulled low when
active. It is used to trigger the
mute function of an external PA
system.
PA mute
A remote switch can be used to
enable or disable the auxiliary
input.
Remote Auxiliary Switch

Page 2-4 GMA 347 Installation Manual
Revision A 190-00325-01
2.5.2 Software Configuration Options
The following list shows the software configurations available for the GMA 347. Configuration program
instructions are found in section 5.
Function and Purpose Software Configuration
Audio Inputs. Allow or disable the
use of external receivers
Enable or Disable DME, ADF, COM3, Play, PA,
SPKR, TEL, and Split COM
Defeate the (MASQ) Master
Squelch feature
Deactivate MASQ
Telephone. Remove telephone
capability
Disable Telephone Channel
Sidetone. Disable the sound of
transmission in the headset
Enable or Disable Sidetone
COM MUTE ON TX Can be disabled. Audio on unselected COMs is
muted while the selected COM is transmitting
audio
COM MUTE ON RX Can be disabled. Audio on unselected COMs is
muted while the selected COM is receiving audio
Audio level. Volume control
adjustment
Adjust Audio level of Music 1 and Music 2,
Unswitched 1, Unswitched 2, Unswitched 3 and
Altitude Warning, SPKR, Pilot and Copilot Mic
Volume, Master Squelch Threshold, and Marker
volume
Marker Threshold Marker Beacon threshold levels are adjustable for
HI and LO sense
ICS Mute ICS Muting of Music 1 can be enabled or disabled
Record Com2 Pilot or Copilot COM recording. During the Split
Com mode, COM 1 or COM 2 audio can be
selected for voice recording and playback
2.5.1 Transmit Interlock and Split COM Operation
NOTE
Garmin makes no expressed or implied guarantees regarding the
suitability of the Split COM feature in any given installation.
In small aircraft, COM and Nav receiver interference is affected by both the distance between antennas
and the tuned frequency separation.
With transmit interlock activated in either the GMA 347 or the COM transceivers, Split COM operation
between a flight crew of more than one pilot is affected.
In aircraft that have a transmit interlock feature, when either transmitter is keyed, all other receivers are
muted so that they won’t pick up interference from the active COM transmitter. This is the preferred
option for single pilot operation.
For aircraft with two flight crew members, transmit-interlock would probably interfere with
communications. When the pilot or the copilot transmit, no audio is heard on any other receiver. This