Garmin GTX GTX 330D User manual

190-00734-11 December 2017 Revision 6
GTX 33X and GTX 3X5 ADS-B
Maintenance Manual
Contains Instructions for Continued Airworthiness for STC
SA01714WI
Aircraft make, model, registration number, and serial
number and accompanying STC configuration
information in appendix A must be completed and saved
with aircraft permanent records.

190-00734-11 GTX 33X and GTX 3X5 ADS-B Maintenance Manual
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190-00734-11 GTX 33X and GTX 3X5 ADS-B Maintenance Manual
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RECORD OF REVISIONS
CURRENT REVISION DESCRIPTION
Revision Revision
Date Description
6 12//17
Updated GTX 33/330 software to v8.04
Updated GTX 3X5 main software to v2.12 and ADSB software to v2.10
Added models to bonding table B-1
5 10/05/16
Updated the standard rack part number.
Moved GPS keep alive input requirement to optional interface.
Updated main and ADS-B software to v2.05
4 07/21/16 Added GTX 3X5 vertical mount.
3 03/03/16 Added GTX 3X5 products.
2 09/18/14 Minor edits. Refer to Current Revision Description for details.
1 05/01/13 Initial release.
Section Page Description
3.1 3-2 Removed directions for software v7.01 or earlier
5.1 5-2 Replaced Figure 5-1 with improved troubleshooting flowchart
5.2 5-3 Replaced Figure 5-4 Sheets 1-5 with improved troubleshooting flowcharts.
5.2 5-9 Removed Figure 5-5 Sheet 1-5. Alert messages and faults are covered by Figure 5-4.
B.1 B-2 Added Diamond DA 62, Tecnum P2010, Ruschmeyer R90-230RG, and Slingsby
T67M260 to Table B-1.

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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 $1,000,000 under Section 2410 of the Export Administration Act of
1979. Include this notice with any reproduced portion of this document.
This information in this document is subject to change without notice. Visit Garmin’s Dealer Resource
Center for current updates and supplemental information concerning the operation of Garmin products.
DEFINITIONS OF WARNINGS, CAUTIONS, AND NOTES
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 website at
www.garmin.com/prop65.
WARNING
Perchlorate Material - special handling may apply. Refer to
www.dtsc.ca.gov./hazardouswaste/perchlorate.
CAUTION
The GTX 330/330D and GTX 335/345 units have a special anti-reflective coated display
that is sensitive to waxes and abrasive cleaners. CLEANERS CONTAINING AMMONIA
WILL HARM THE ANTI-REFLECTIVE COATING. It is important to clean the display
using a clean, lint-free cloth, with a cleaner that is safe for anti-reflective coatings.
WARNING
Warnings indicate that immediate attention must be given to avoid potential
equipment damage and personal injury should the instructions be disregarded.
CAUTION
Cautions indicate an alert to potential damage to the equipment if the
procedural step is not directly followed.
NOTE
Notes indicate additional information is needed.

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TABLE OF CONTENTS
1 INTRODUCTION..............................................................................................................................1-1
1.1 Content, Scope, Purpose.............................................................................................................1-1
1.2 Organization ...............................................................................................................................1-1
1.3 Applicability...............................................................................................................................1-2
1.4 Publications ................................................................................................................................1-2
1.5 Revision and Distribution...........................................................................................................1-2
1.6 Reference....................................................................................................................................1-3
2 SYSTEM DESCRIPTION.................................................................................................................2-1
2.1 GTX 330/330D...........................................................................................................................2-2
2.2 GTX 33/33D...............................................................................................................................2-4
2.3 GTX 335/335R...........................................................................................................................2-6
2.4 GTX 345/345R...........................................................................................................................2-8
2.5 GTX 335R/345R with Legacy G1000 .....................................................................................2-10
2.6 Electrical Load Information .....................................................................................................2-11
3 GTX CONTROL AND OPERATION .............................................................................................3-1
3.1 GTX 330/330D...........................................................................................................................3-2
3.2 GTX 335/345..............................................................................................................................3-5
3.3 GTX 33/33D and GTX 335R/345R ...........................................................................................3-8
3.4 GTX 335R/345R with Legacy G1000 .......................................................................................3-9
3.5 GTX 3X5 Install Tool ..............................................................................................................3-12
4 INSTRUCTIONS FOR CONTINUED AIRWORTHINESS.........................................................4-1
4.1 Applicability...............................................................................................................................4-1
4.2 Airworthiness Limitations..........................................................................................................4-1
4.3 Servicing Information ................................................................................................................4-2
4.4 Maintenance Intervals ................................................................................................................4-3
4.5 Visual Inspection........................................................................................................................4-4
4.6 Electrical Bonding Test..............................................................................................................4-6
4.7 Additional Instructions...............................................................................................................4-6
5 TROUBLESHOOTING ....................................................................................................................5-1
5.1 GTX General Troubleshooting...................................................................................................5-1
5.2 GTX Failure Annunciations .......................................................................................................5-3
5.3 GTX 33X Connector Pinout Information.................................................................................5-14
5.4 GTX 3X5 Connector Pinout Information.................................................................................5-19
6 UNIT REMOVAL AND REINSTALLATION...............................................................................6-1
6.1 GTX 330/330D...........................................................................................................................6-1
6.2 GTX 33/33D...............................................................................................................................6-3
6.3 GTX 3X5....................................................................................................................................6-4
6.4 Transponder Antenna ...............................................................................................................6-15
7 SOFTWARE.......................................................................................................................................7-1
7.1 Software Check ..........................................................................................................................7-1
7.2 GTX 33/330 Software Update....................................................................................................7-6
7.3 GTX 3X5/3X5R Software Update .............................................................................................7-8
8 SYSTEM CONFIGURATION AND CHECKOUT .......................................................................8-1
8.1 Overview ....................................................................................................................................8-1
8.2 System Checkout........................................................................................................................8-1
8.3 GTX 33/330 Configuration ........................................................................................................8-1
8.4 GTX 3X5 Configuration ............................................................................................................8-2
8.5 GTX Airborne Test Mode ..........................................................................................................8-4

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8.6 Regulatory Test ..........................................................................................................................8-6
8.7 ADS-B Out Test .........................................................................................................................8-7
8.8 GTX 3X5 with TCAS System Test (GX000 Only) ...................................................................8-8
9 SYSTEM RETURN TO SERVICE PROCEDURE........................................................................9-1
9.1 Maintenance Records .................................................................................................................9-1
APPENDIX A INSTALLATION SPECIFIC INFORMATION.........................................................A-1
APPENDIX B SPECIAL BONDING PROCEDURES........................................................................ B-1
B.1 Considerations for Untreated or Bare Dissimilar Metals .......................................................... B-1
B.2 Preparation of Aluminum Surfaces ........................................................................................... B-4
B.3 Composite Aircraft.................................................................................................................... B-4
B.4 Tube and Fabric Aircraft ........................................................................................................... B-9
B.5 Bonding Jumper ...................................................................................................................... B-12

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LIST OF FIGURES
Figure 2-1 GTX 330 or GTX 330D Interface Summary ........................................................................2-3
Figure 2-2 GTX 33 or GTX 33D Interface Summary ............................................................................2-5
Figure 2-3 GTX 335 or GTX 335R Interface Summary ........................................................................2-7
Figure 2-4 GTX 345 or GTX 345R Interface Summary ........................................................................2-9
Figure 2-5 GTX 335R or GTX 345R Interface Summary with Legacy G1000 ...................................2-10
Figure 3-1 GTX 330/330D Front Panel ..................................................................................................3-2
Figure 3-2 GTX 335/345 Front Panel ....................................................................................................3-5
Figure 3-3 GTN 7XX Transponder Control ...........................................................................................3-8
Figure 3-4 GTN 6XX Transponder Control ...........................................................................................3-8
Figure 3-5 GNS 480 Transponder Control .............................................................................................3-9
Figure 3-6 G1000 Transponder Control ...............................................................................................3-10
Figure 3-7 G1000 Transponder Control ...............................................................................................3-11
Figure 3-8 USB A and USB B Connectors ..........................................................................................3-12
Figure 3-9 GTX 3X5/3X5R State Page ................................................................................................3-13
Figure 3-10 GTX 3X5/3X5R Status Page ..............................................................................................3-14
Figure 3-11 GTX 3X5/3X5R Configuration Group ...............................................................................3-15
Figure 3-12 GTX 3X5/3X5R Diagnostics Group ..................................................................................3-17
Figure 3-13 GTX 3X5/3X5R Product Data Group ................................................................................3-18
Figure 5-1 GTX (All Models) Transponder Troubleshooting ................................................................5-2
Figure 5-2 GTX 330/330D Transponder Failure/Fault Messages ..........................................................5-3
Figure 5-3 GTX 33/33D Transponder Failure/Fault Messages ..............................................................5-4
Figure 5-4 GTX 3X5 Transponder Alerts ..............................................................................................5-5
Figure 5-5 GTX 3X5 Install Tool Failure/Fault MessagesTransponder Alerts .....................................5-9
Figure 5-6 Rear View, Connector P3301 .............................................................................................5-14
Figure 5-7 GTX 33/330 ARINC 429 Connections ...............................................................................5-18
Figure 5-8 Rear View, Connector J3251 ..............................................................................................5-19
Figure 5-9 Rear View, Connector J3252 ..............................................................................................5-21
Figure 6-1 GTX 330 Mounting Rack/Connector Assembly ..................................................................6-2
Figure 6-2 GTX 33 Mounting Rack/Connector Assembly ....................................................................6-3
Figure 6-3 GTX 3X5 Connector Kits .....................................................................................................6-4
Figure 6-4 GTX 3X5 without GPS Back Plate Assembly (P/N 011-02976-00) ....................................6-5
Figure 6-5 GTX 3X5 with GPS Back Plate Assembly (P/N 011-02976-01) .........................................6-5
Figure 6-6 GTX 3X5 Vertical Mount without GPS, Back Plate Assembly (P/N 011-02976-10) .........6-6
Figure 6-7 GTX 3X5 Vertical Mount with GPS, Back Plate Assembly (P/N 011-02976-11) ..............6-7
Figure 6-8 GTX 3X5 Vertical Mount with TNC XPDR Back Plate Assembly
(P/N 011-02976-12) ...................................................................................................................................6-7
Figure 6-9 GTX 3X5 Mounting Rack/Connector Assembly .................................................................6-9
Figure 6-10 GTX 3X5R Standard Mounting Rack/Connector Assembly ..............................................6-11
Figure 6-11 GTX 3X5R G1000 Mounting Rack/Connector Assembly .................................................6-11
Figure 6-12 GTX 3X5R Vertical Mounting Rack/Connector Assembly ...............................................6-13
Figure 6-13 Garmin Altitude Encoder with Back Plate Assembly ........................................................6-15
Figure 7-1 GTX 330 Start-Up Screen ....................................................................................................7-1
Figure 7-2 GTX 330 Product Data Page ................................................................................................7-2
Figure 7-3 GTX 3X5 Start-Up Screen ....................................................................................................7-3
Figure 7-4 GTX 3X5 Product Data Page ...............................................................................................7-3
Figure 7-5 GTN 6XX/7XX System Page ...............................................................................................7-4
Figure 7-6 GX000 System Status Page ..................................................................................................7-5
Figure 7-7 Software Update Connection ................................................................................................7-6

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Figure 7-8 GTX 3X5 Install Tool Software Upload Page ......................................................................7-9
Figure B-1 Electrical Bonding Preparation – Nut Plate ......................................................................... B-1
Figure B-2 Electrical Bonding Preparation – Bolt/Nut Joint ................................................................. B-1
Figure B-3 Electrical Bond Preparation – Terminal Lug ....................................................................... B-1
Figure B-4 Fiberglass Insulation for Carbon Material ...........................................................................B-5
Figure B-5 Aluminum Tape Joint .......................................................................................................... B-6
Figure B-6 Aluminum Tape Ground Termination ................................................................................. B-7
Figure B-7 Remote GTX Aluminum Tape Installation ......................................................................... B-8
Figure B-8 Electrical Bonding Using Conductive Clamp .................................................................... B-11
Figure B-9 Bonding Strap .................................................................................................................... B-13

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LIST OF TABLES
Table 1-1 Reference Documentation ....................................................................................................1-2
Table 2-1 GTX Electrical Load ...........................................................................................................2-11
Table 4-1 Maintenance Intervals ...........................................................................................................4-3
Table 5-1 GTX 33X Pinout .................................................................................................................5-14
Table 5-2 GTX 33X Encoded Altitude Pin Assignments ...................................................................5-16
Table 5-3 GTX 33/330 Discrete Outputs ............................................................................................5-17
Table 5-4 GTX 33/330 Discrete Inputs ...............................................................................................5-17
Table 5-5 GTX 33/330 RS-232 Connections ......................................................................................5-17
Table 5-6 J3251 Pinout .......................................................................................................................5-19
Table 5-7 J3252 Pinout .......................................................................................................................5-21
Table 5-8 GTX 3X5/3X5R Encoded Altitude Pin Assignments ........................................................5-22
Table 5-9 GTX 3X5/3X5R Discrete Outputs ......................................................................................5-23
Table 5-10 GTX 3X5/3X5R Configurable Output Pins .......................................................................5-24
Table 5-11 GTX 3X5/3X5R Discrete Inputs ........................................................................................5-25
Table 5-12 GTX 3X5/3X5R Configurable Input Pins ..........................................................................5-26
Table 5-13 GTX 3X5/3X5R RS-232 Connections ...............................................................................5-26
Table 5-14 GTX 3X5/3X5R ARINC 429 Connections ........................................................................5-27
Table 5-15 GTX 3X45/3X45R RS-422 Connections ...........................................................................5-27
Table 5-16 GTX 345/345R HSDB Connections ...................................................................................5-28
Table 6-1 GTX 3X5 Connector Kit Hardware ......................................................................................6-4
Table 6-2 Standard/G1000 Mount Back Plate Hardware .....................................................................6-4
Table 6-3 Vertical Mount Back Plate Hardware ...................................................................................6-6
Table 6-4 Garmin Altitude Encoder Kit - P/N 011-03080-00 ............................................................6-15
Table 8-1 Ramp Test Pressure Altitude Check Scenario ......................................................................8-8
Table B-1 Ground Plane Definitions and Ground Path Resistance Requirements ............................... B-2
Table B-2 Composite Airframe Bonding Hardware ............................................................................. B-6
Table B-3 Tube and Fabric Airframe Bonding Hardware .................................................................. B-10
Table B-4 Airframe Bonding Hardware ............................................................................................. B-13

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1 INTRODUCTION
1.1 Content, Scope, Purpose .....................................................................................................1-1
1.2 Organization........................................................................................................................ 1-1
1.3 Applicability ....................................................................................................................... 1-2
1.4 Publications......................................................................................................................... 1-2
1.5 Revision and Distribution ...................................................................................................1-2
1.6 Reference ............................................................................................................................ 1-3
1.6.1 Terminology.................................................................................................................. 1-3
1.6.2 Acronyms...................................................................................................................... 1-3
1.1 Content, Scope, Purpose
This document provides Instructions for Continued Airworthiness (ICA) of the GTX 33X and GTX 3X5 with
ADS-B functionality installed and compliant to ADS-B Out version 2, under AML STC SA01714WI. This
document satisfies the requirements for continued airworthiness as defined by 14 CFR Part 23.1529 and
appendix G. Information in this document is required to maintain the continued airworthiness of the GTX 33X
and GTX 3X5.
1.2 Organization
The following outline briefly describes the organization of this manual.
Section 2: System Overview
Provides a description of the GTX 33X and GTX 3X5 equipment installed by this STC.
Section 3: Control and Operation
Provides basic control and operation information specifically tailored to maintenance practices.
Section 4: Instructions for Continued Airworthiness
Provides instructions for continued airworthiness of the GTX 33X and GTX 3X5 ADS-B units.
Section 5: Troubleshooting
Provides troubleshooting information to aid in diagnosing and resolving problems with GTX 33X and
GTX 3X5 system equipment.
Section 6: Unit Removal and Reinstallation
Provides instructions for the removal and replacement of GTX 33X and GTX 3X5 ADS-B units.
Section 7: Software
Provides instructions for loading software on GTX 33X and GTX 3X5 ADS-B units.
Section 8: System Configuration and Checkout
Provides instructions for configuring and testing of GTX 33X and GTX 3X5 system equipment.
Section 9: System Return to Service Procedure
Specifies return-to-service procedures to be performed upon completion of maintenance to GTX 33X and
GTX 3X5 system equipment.
APPENDIX A: Aircraft Specific Information
Provides a template to record aircraft specific installation and configuration data for GTX 33X and
GTX 3X5 system equipment.
APPENDIX B: Special Bonding Procedures
Provides instructions for achieving an electrical bond with GTX 33X and GTX 3X5 system equipment.

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1.3 Applicability
This document applies to all aircraft with either the GTX 33X or the GTX 3X5 installed in accordance with
STC SA01714WI. Modification of an aircraft by this Supplemental Type Certificate (STC) obligates the
aircraft operator to include the maintenance information provided by this document in the operator’s
Aircraft Maintenance Manual and the operator’s Aircraft Scheduled Maintenance Program.
1.4 Publications
In addition to this manual, the following documents are recommended to perform maintenance based on
the installed and interfaced equipment. It is the responsibility of the owner/operator to ensure the latest
applicable versions of these documents are used during operation, servicing, or maintenance of the
airplane.
Table 1-1 Reference Documentation
1.5 Revision and Distribution
This document is required for maintaining the continued airworthiness of the aircraft. Garmin Dealers may
obtain the latest revision of this document at the Garmin Dealer Resource Center, website.
Dealers are notified of manual revision changes via a Garmin Service Bulletin.
Owner and operators may obtain the latest revision of this document at www.flyGarmin.com or by
contacting a Garmin dealer. Garmin contact information is available at www.flyGarmin.com.
Document Garmin P/N
GTX 33X and GTX 3X5 ADS-B AML STC Equipment List 005-00734-05
GTN 625/635/650 Pilot’s Guide 190-01004-03
AFMS, GTX 33X and GTX 3X5 AML STC 190-00734-15
GTN 725/750 Pilot’s Guide 190-01007-03
GNS 400W Series Installation Manual 190-00356-08
GNS 500W Series Installation Manual 190-00357-08
GNS 480 (CNX80) Color GPS/NAV/COM Installation Manual 560-0982-01
GNS 480 Pilot’s Guide 190-00502-00
G1000 System Installation Manual 190-00303-00
GTN 6XX/7XX Part 23 AML STC Installation Manual 190-01007-A3
GTX 3XX Part 23 AML STC Installation Manual 190-00734-10

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1.6 Reference
1.6.1 Terminology
Except where specifically noted, references made to the GTX 33X or GTX 3X5 will apply to the
GTX 330/330D/33/33D or GTX 335/335R/345/345R respectively.
ADS-B or ADS-B Out refers to version 2 ADS-B Out only.
ADS-B In refers to TIS-B traffic and FIS-B weather received from ground stations over UAT as well as
ADS-B and ADS-R traffic targets received directly over 1090 MHz or UAT.
Throughout this document references will be made to metallic aircraft. For the purposes of this manual,
metallic aircraft will be those with an aluminum skin. Nonmetallic aircraft refers to all other aircraft
(e.g., wooden aircraft, aircraft with composite skin, or aircraft with tube and fabric construction).
Unless otherwise stated, all units of measure are US standard units.
The term squitter refers to a burst or broadcast of aircraft-tracking data that is transmitted periodically by a
Mode S transponder without interrogation from a controller’s radar.
1.6.2 Acronyms
AC: Advisory Circular ICA: Instructions for Continued Airworthiness
ADC: Air Data Computer ICAO: International Civil Aviation Organization
ADS-B: Automatic Dependent Surveillance -
Broadcast
I/O: Input/Output
AHRS: Attitude Heading Reference System MFD: Multifunction Display
AML: Approved Model List PED: Portable Electronic Device
ATC: Air Traffic Control SBAS: Satellite-Based Augmentation System
ATCRBS: Air Traffic Control Radar Beacon System SPI: Special Position Identifier
EGNOS: European Geostationary Navigation
Overlay Service
SRM: Structural Repair Manual
ES: Extended Squitter STC: Supplemental Type Certificate
FAA: Federal Aviation Administration TAS: Traffic Advisory System
FIS-B: Flight Information System-Broadcast TCAS: Traffic Alert and Collision Avoidance
System
GAE: Garmin Altitude Encoder TIS: Traffic Information Service
GNS: Garmin Navigation System TSO: Technical Standard Order
GNSS: Global Navigation Satellite System UAT: Universal Access Transceiver
GPS: Global Positioning System VSWR: Voltage Standing Wave Ratio
GTN: Garmin Touchscreen Navigator WAAS: Wide Area Augmentation System
GTX: Garmin Transponder

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2 SYSTEM DESCRIPTION
2.1 GTX 330/330D ................................................................................................................... 2-2
2.2 GTX 33/33D ....................................................................................................................... 2-4
2.3 GTX 335/335R ................................................................................................................... 2-6
2.4 GTX 345/345R ................................................................................................................... 2-8
2.5 GTX 335R/345R with Legacy G1000 .............................................................................. 2-10
2.6 Electrical Load Information.............................................................................................. 2-11
Garmin GTX 33X and GTX 3X5 units operate on radar frequencies, receiving ground radar or TCAS
interrogations. The GTX transmits a coded response of pulses to ground-based radar on a frequency of
1090 MHz. Each unit has IDENT capability and replies to ATCRBS Mode A, Mode C and Mode S
All-Call interrogation. The GTX 345/345R units include ADS-B In which provides TIS-B and FIS-B data
via UAT and 1090 MHz. The GTX 3X5 units offer an optional Garmin altitude encoder to meet the
required barometric pressure altitude source and an optional internal GPS/SBAS source to meet the
required GNSS position source integrity for ADS-B Out.
The Garmin transponders approved by this STC are in the family of GTX 33X and GTX 3X5 transponders.
The ES option of the GTX 33X units provides ADS-B extended squitter functionality.
The GTX 33X models include:
GTX 33
GTX 330
GTX 33D
GTX 330D
The GTX 3X5 units all provide ADS-B Out functionality. GTX 345/345R units provide ADS-B In.
The GTX 3X5 models include:
GTX 335
GTX 345
GTX 335R
GTX 345R
ADS-B technology improves situational awareness and flight safety. A Garmin transponder with ADS-B
capabilities will automatically transmit position, velocity, and heading information to other aircraft and
ground stations. The current air traffic control system depends on a transponder request for pertinent
aircraft information, whereas ADS-B provides automatic transmission of aircraft information without a
request.

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2.1 GTX 330/330D
GTX 330/330D units are stand alone, panel mounted units that operate through the integrated display.
GTX 330/330D units can be controlled by an external control unit such as the GTN 6XX/7XX or the
GNS 480. They can display TIS-A information on an approved display unit, via an RS-232 digital
interface.
GTX 330/330D units provide the following features.
Mode S transponder
ADS-B Out capability
Entry and display of squawk code and flight ID
Display of pressure altitude
Display of density altitude
Display of outside air temp
Display of flight timers
Audio output
TIS-A traffic output to a compatible display
The transponder annunciates when the unit has an ADS-B Out failure to alert the crew that the unit has a
degraded ADS-B system.
GTX 330/330D units communicate through the following interfaces.
ARINC 429
RS-232
Gray code
Discrete I/O
Power is provided by the aircraft’s existing avionics bus. Non-diversity GTX 330 units interface with a
transponder antenna mounted to the bottom of the fuselage. GTX 330D diversity units interface to a
transponder antenna mounted to the top of the fuselage as well as the antenna mounted to the bottom.
Figure 2-1 provides a summary of the interfaces provided for the GTX 330 or GTX 330D. Refer to
GTX 3XX Part 23 AML STC Installation Manual for interfaces allowed under this STC.

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Figure 2-1 GTX 330 or GTX 330D Interface Summary
GTX 330
or
GTX 330D
Bottom Antenna
GTX 330D
Installs Only
Traffic System
Audio Panel
Optional Interfaces
Heading Source
Secondary GPS
Display
Required Interfaces
Altitude Source
Power/Ground
Top Antenna
GPS
Temperature
Squat Switch
External STBY
External Ident
Radar Altitude

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2.2 GTX 33/33D
GTX 33/33D units are remote mounted and require a display/control interface as provided by the
GTN 6XX/7XX or GNS 480 in order to be installed in accordance with this STC. Basic transponder
functions of the GTX 33/33D are identical to the GTX 330/330D.
GTX 33/33D units provide the following features.
Mode S transponder
ADS-B Out capability
Entry and display of squawk code and flight ID*
Display of pressure altitude*
Display of density altitude*
Display of outside air temp*
Display of flight timers*
Audio output
TIS-A traffic output to a compatible display
*Requires supported external control and display system.
The transponder annunciates when the unit has an ADS-B Out failure to alert the crew that the unit has a
degraded ADS-B system.
GTX 33/33D units communicate through the following interfaces.
ARINC 429
RS-232
Gray code
Discrete I/O
Power is provided by the aircraft’s existing avionics bus. Non-diversity GTX 33 units interface with a
transponder antenna mounted to the bottom of the fuselage. GTX 33D units interface to a transponder
antenna mounted to the top of the fuselage as well as an antenna mounted to the bottom.
Figure 2-2 provides a summary of the interfaces provided for the GTX 33 or GTX 33D. Refer to
GTX 3XX Part 23 AML STC Installation Manual for interfaces allowed under this STC.

190-00734-11 GTX 33X and GTX 3X5 ADS-B Maintenance Manual
Rev. 6 Page 2-5
Figure 2-2 GTX 33 or GTX 33D Interface Summary
GTX 33
or
GTX 33D
Bottom Antenna
GTX 33D
Installs Only
Garmin
GTN 6XX/7XX
Or
GNS 480
Traffic System
Audio Panel
Optional Interfaces
Heading Source
Secondary GPS
Temperature
Squat Switch
Required Interfaces
Altitude Source
Power/Ground
Top Antenna
External Ident
External Standby
Radar Altitude

190-00734-11 GTX 33X and GTX 3X5 ADS-B Maintenance Manual
Rev. 6 Page 2-6
2.3 GTX 335/335R
The GTX 335/335R units are panel or remote mounted units providing Mode S with ADS-B Out extended
squitter capability. The panel mounted unit contains an integrated display while the remote mounted unit
requires an interface to a control source for normal operation and functionality.
GTX 335/335R units provide the following features.
Mode S transponder
ADS-B Out capability
Optional internal GNSS receiver
Optional altitude encoder module
Entry and display of squawk code and flight ID
Display of pressure altitude
Display of outside air temp
Display of density altitude
Display of flight timers
Audio output
TIS-A traffic output to a compatible display
The transponder annunciates when the unit has an ADS-B Out failure to alert the crew that the unit has a
degraded ADS-B system.
GTX 335/335R units communicate through the following interfaces.
ARINC 429
RS-232
Gray code
Discrete I/O
Figure 2-3 provides a summary of the interfaces provided for the GTX 335 or GTX 335R. Refer to
GTX 3XX Part 23 AML STC Installation Manual for interfaces allowed under this STC.

190-00734-11 GTX 33X and GTX 3X5 ADS-B Maintenance Manual
Rev. 6 Page 2-7
Figure 2-3 GTX 335 or GTX 335R Interface Summary
GTX 335/335R
GPS Antenna
GPS Source
Audio Panel
Bottom Antenna
GTX 3X5 with GPS only
GTX 335R Control
Power/Ground
Altitude Source
Heading Source
Air Data Source
Secondary GPS
Radio Altitude
Source
Existing LRUNew LRU
Legend
Optional Interfaces Required Interfaces
Squat Switch
Garmin Altitude
Encoder
OR
Temperature
External Ident
External Standby
Traffic System
For XPDR Cross-Talk
Keep Alive Input

190-00734-11 GTX 33X and GTX 3X5 ADS-B Maintenance Manual
Rev. 6 Page 2-8
2.4 GTX 345/345R
The GTX 345/345R units are panel or remote mounted units providing Mode S with ADS-B Out extended
squitter, and UAT and 1090 receivers for ADS-B In capabilities. The panel mounted unit contains an
integrated display while the remote mounted units require an interface to a control source for normal
operation and functionality.
GTX 345/345R units provide the following features.
Mode S transponder
ADS-B Out capability
ADS-B In capability with built-in 1090 MHz and UAT receivers
Optional internal GNSS receiver
Optional altitude encoder module
Entry and display of squawk code and flight ID
Display of pressure altitude
Display of outside air temp
Display of density altitude
Display of flight timers
Audio output
Bluetooth interface for display of weather and traffic on portable devices
The transponder annunciates when the unit has an ADS-B failure to alert the crew that the unit has a
degraded ADS-B In or ADS-B Out system.
GTX 345/345R units communicate through the following interfaces.
HSDB
ARINC 429
RS-232
RS-422
Gray code
Discrete I/O
Figure 2-4 provides a summary of the interfaces provided for the GTX 345 or GTX 345R. Refer to
GTX 3XX Part 23 AML STC Installation Manual for interfaces allowed under this STC.