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Garmin International, Inc.
1200 E. 151st Street
Olathe, KS 66062 USA
Telephone: 913.397.8200
Aviation Panel-Mount Technical Support Line (Toll Free) 1.888.606.5482
www.garmin.com
Garmin (Europe) Ltd.
Liberty House, Hounsdown Business Park
Southampton, Hampshire SO40 9LR U.K.
+44/ (0) 370 850 1243
Garmin AT, Inc.
2345 Turner Rd., SE
Salem, OR 97302 USA
Telephone: 503.581.8101
AVIATION LIMITED WARRANTY
GTX 23 warranty information is available at garmin.com/aviationwarranty.
RECORD OF REVISIONS
RevisionRevision DateDescription
A08/31/2011Initial release
B09/11/2012Updated for SW v7.01
C06/06/14Updated mounting rack info
D09/22/14Updated TSO and configuration info
E04/08/15Corrected SW part numbers
F10/20/15Updated SW and CLD part numbers
G01/03/18Updated Transponder Capabilities info
190-00906-01GTX 23 Installation Manual
Rev. GPage A
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. The preceding statement is required to be included on any and all
reproductions in whole or in part of this manual.
CURRENT REVISION DESCRIPTION
Revision
G
Page
Number(s)
iiiFrontAdded Software License Agreement
1-11.2Updated Equipment Description
1-51.7.1Added continuous operation spec to Table 1-2
4-44.2.2Updated active low description in Table 4-4
4-54.3.1Updated RS-232 description
C-1–C-12Appdx C
C-2Appdx CUpdated Figure C-2
Section
Number
Description of Change
Removed Appendix C (Compliance Matrix) from previous
revision
190-00906-01GTX 23 Installation Manual
Rev. GPage i
DEFINITIONS OF WARNINGS, CAUTIONS, AND NOTES
WARNING
WARNING
WARNING
Warni ngs are used to bring to the installer’s immediate attention that not only
damage to the equipment but personal injury may occur if the instruction is
disregarded.
CAUTION
Cautions are used to alert the individual that damage to equipment may
result if the procedural step is not followed to the letter.
NOTE
Notes are used to expand and explain the preceding step and provide further
understanding of the reason for the particular operation.
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
Perchlorate Material – special handling may apply. See www.dtsc.ca.gov/hazardouswaste/
perchlorate.
.
190-00906-01GTX 23 Installation Manual
Rev. GPage ii
SOFTWARE LICENSE AGREEMENT
BY USING THE DEVICE, COMPONENT OR SYSTEM MANUFACTURED OR SOLD BY GARMIN
(“THE GARMIN PRODUCT”), YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS
OF THE FOLLOWING SOFTWARE LICENSE AGREEMENT. PLEASE READ THIS AGREEMENT
CAREFULLY. Garmin Ltd. and its subsidiaries (“Garmin”) grants you a limited license to use the
software embedded in the Garmin Product (the “Software”) in binary executable form in the normal
operation of the Garmin Product. Title, ownership rights, and intellectual property rights in and to the
Software remain with Garmin and/or its third-party providers. You acknowledge that the Software is the
property of Garmin and/or its third-party providers and is protected under the United States of America
copyright laws and international copyright treaties. You further acknowledge that the structure,
organization, and code of the Software are valuable trade secrets of Garmin and/or its third-party providers
and that the Software in source code form remains a valuable trade secret of Garmin and/or its third-party
providers. You agree not to reproduce, decompile, disassemble, modify, reverse assemble, reverse
engineer, or reduce to human readable form the Software or any part thereof or create any derivative works
based on the Software. You agree not to export or re-export the Software to any country in violation of the
export control laws of the United States of America.
190-00906-01GTX 23 Installation Manual
Rev. GPage iii
TABLE OF CONTENTS
PARAGRAPHPAGE
Section 1 GENERAL DESCRIPTION .............................................................1-1
Appendix C INTERCONNECT DRAWINGS (Example Only) ...................C-1
Appendix D OUTLINE AND INSTALLATION DRAWINGS ....................D-1
190-00906-01GTX 23 Installation Manual
Rev. GPage vii
1 GENERAL DESCRIPTION
NOTE
1.1 Introduction
This manual is intended to provide mechanical and electrical information for use in the planning and
design of an installation of the GTX 23 into an aircraft. This manual is not a substitute for an approved
airframe-specific maintenance manual, installation design drawing, or complete installation data package.
Attempting to install equipment by reference to this manual alone and without first planning or designing
an installation specific to your aircraft may compromise your safety and is not recommended. The content
of this manual assumes use by competent and qualified avionics engineering personnel and/or avionics
installation specialists using standard aviation maintenance practices in accordance with Title 14 of the
Code of Federal Regulations and other relevant accepted practices. This manual is not intended for use by
individuals who do not possess the competencies and abilities set forth above.
Garmin recommends installation of the GTX 23 by a Garmin-authorized installer. To the
extent allowable by law, Garmin will not be liable for damages resulting from improper or
negligent installation of the GTX 23. For questions, please contact Garmin Aviation
Product Support at 1-888-606-5482.
1.2 Equipment Description
The Garmin GTX 23 rack-mounted Mode S Transponder is a radio transmitter and receiver that operates
on radar frequencies, receiving ground radar and TCAS interrogations at 1030 MHz and transmitting a
coded response of pulses on a frequency of 1090 MHz. The GTX 23 is equipped with IDENT capability
that activates the Special Position Identification (SPI) pulse for 18 seconds.
The GTX 23 replies to Mode A, Mode C and Mode S interrogations. Mode A replies consist of framing
pulses and any one of 4,096 codes, which differ in the position and number of pulses transmitted. Mode C
replies include framing pulses and encoded altitude. Mode S interrogations are selective. The Mode S
transponders can respond to a single directed interrogation from the ground station or another aircraft.
The GTX 23 with Extended Squitter Enabled provides Automatic Dependent Surveillance-Broadcast
(ADS-B) technology that improves situational awareness and flight safety. With ADS-B capabilities,
position, velocity, and heading information are automatically transmitted to other aircraft and ground
stations. The current air traffic control system depends on the transmission of interrogations for pertinent
aircraft information at a slower update rate. ADS-B provides immediate surveillance of air-to-air traffic
and aircraft in remote or inhospitable areas not currently covered by radar.
The GTX 23 is a Level 2 transponder, providing downlink of aircraft information. Ground stations can
interrogate Mode S Transponders individually using a 24-bit ICAO Mode S address, which is unique to the
particular aircraft. In addition, ground stations may interrogate a GTX 23 for its Transponder data
capability and the aircraft's Flight ID, which is the registration number or other call sign. The GTX 23
makes the maximum airspeed capability (set during configuration setup) available to TCAS systems
on-board nearby aircraft to aid in the determination of TCAS advisories. The GTX 23 also supports
receiving TIS services from ground stations.
The GTX 23 meets Mode S Enhanced Surveillance (EHS) requirements. Mode S Enhanced Surveillance is
used predominantly in European airspace. It provides information consisting of additional aircraft
parameters (see CS-ACNS and AMC 20-13) to ground radar systems. Compliance with Enhanced
Surveillance may require additional interface between aircraft systems and the GTX 23.
The GTX 23 provides the capabilities of Automatic Dependent Surveillance-Broadcast (ADS-B)
technology, which improves situational awareness and flight safety. With ADS-B capabilities, position,
velocity, and heading information are automatically transmitted to other aircraft and ground stations. The
current air traffic control system depends on a transponder request for pertinent aircraft information.
ADS-B provides automatic transmission of aircraft information without a request.
1.3.1ADS-B Versions
There are three distinct ADS-B versions recognized by regulatory authorities. As shown in the table
below, the Garmin GTX 23 w/ES currently supports ADS-B Out 1090MHz Extended Squitter capability
meeting ‘Version 1’ or ‘Version 2' ADS-B system requirements depending on software version
(Table 1-1).
Table 1-1 ADS-B Versions
ADS-B
Version
Version 1Yes6.00 - 6.20Equipment designed to (E)TSO-166a / RTCA DO-260A
Version 2*Yes
*Version required by 2020 ADS-B Out mandate defined in 14 CFR 91.225
GTX 23
w/ES
Compliant
Supported
SW Version
7.01
and later
Regulatory Standard/Minimum Performance
Specification
Equipment designed to TSO-166b / RTCA DO-260B
1.3.1.1Installation Approval of Version 2 ADS-B Systems
GTX 23 w/ES transponders running software versions v7.01 and later support Version 2 ADS-B Out
functionality.
There are two options for installers wanting to install GTX 23 w/ES transponders running software
versions v7.01 and later:
1. Installers may elect to disable the ADS-B Extended Squitter function, as described in Section 3.8
2. Installers must utilize a Supplemental Type Certificate (STC) for the GTX 23 with the Version 2
ADS-B Extended Squitter activated.
It is the installer’s responsibility to ensure the ADS-B Out system is compliant with
AC 20-165 and to ensure compatibility between the GTX 23 and the ADS-B Out position
source equipment. See Garmin ADS-B Out Compatible Equipment (190-01533-00) for
compatible equipment shown to be eligible for 14 CFR 91.227-compliant installations in
accordance with AC 20-165
Traffic Information Service (TIS) provides a graphic display of traffic advisory information in the cockpit
for non-TCAS equipped aircraft.
TIS is a ground-based service providing relative location of all transponder equipped aircraft within a
specified service volume. The TIS ground sensor uses real time track reports to generate traffic
notification.
Traffic display is available to aircraft equipped with a Mode S data link such as the Garmin GTX 23
transponder. Traffic can then be displayed on a Garmin GDU Primary Flight Display, or GNS 400W/
500W-series unit.
Surveillance data includes all transponder equipped aircraft within the coverage volume. Aircraft without
an operating transponder are invisible to TIS. TIS displays traffic within seven nautical miles from 3000
feet below to 3500 feet above the requesting aircraft.
Other equipment on board the aircraft may transmit in the same frequency band as the transponder. DME,
TCAS, or another transponder are examples of equipment that operate in the same frequency band. Mutual
suppression is a synchronous pulse that is sent to the other equipment to suppress transmission of a
competing transmitter for the duration of the transmission. The transponder transmission is suppressed by
an external source, and other equipment on board that transmit in the same frequency band are suppressed
by the GTX 23 transponder. This feature is designed to limit mutual interference.
1.6 Interface Summary
The GTX 23 provides the following interface connections via the rear connector. See Section 4 and
Appendix C for connection details.
•External IDENT input
•External STBY input (useful for dual transponder installations)
•External mutual suppression pulse input/output
•Aircraft power input (14/28 Vdc)
•RS-232 input #1 connection for altitude and unit control data
•RS-232 output #1 connection for TIS and unit status
•RS-232 input #2 connection for GPS data for ADS-B
•Supports Comm-A and Comm-B protocol
•ARINC 429 outputs for TIS data
•ARINC 429 input
The GTX 23 supports the following list of Comm-B Definition Subfield (BDS) registers:
•BDS (0,0) Air Initiated Comm-B (AICB)
•BDS (0,5) Extended Squitter Airborne Position (ES Enable Units Only)
•BDS (0,6) Extended Squitter Surface Position (ES Enable Units Only)
•BDS (0,7) Extended Squitter Status Position (ES Enable Units Only)
•BDS (0,8) Extended Squitter Aircraft Identification and Category (ES Enable Units Only)
•BDS (0,9) Extended Squitter Airborne Velocity – Subtypes 1 and 3 (ES Enable Units Only)
•BDS (0,A) Extended Squitter Event Driven Data (ES Enable Units Only)
•BDS (1,0) Data Link Capability Report
•BDS (1,7) Common Usage Ground Initiated Comm-B (GICB) Capability Report
•BDS (1,8) Mode S Specific Services GICB Capability Report
•BDS (1,9) Mode S Specific Services GICB Capability Report
•BDS (1,D) Mode S Specific Services Protocols (MSP) Capability Report
•BDS (2,0) Aircraft Identification
•BDS (4,0) Selected Vertical Intention
•BDS (5,0) Track and Turn Report
•BDS (6,0) Heading and Speed Report
•BDS (6,1) Emergency/Priority Status (ES Enable Units Only)
•BDS (6,2) Target State and Status (ES Enabled Units Only, software versions v8.01 and later)
•BDS (6,5) Aircraft operational Status (ES Enable Units Only)
Note 1: Each supported UF Format interrogation will illicit the corresponding DF format response. There
is no response to the following UF formats: 1, 2, 3, 6, 7, 8, 9, 10, 12, 13, 14, 15, 17, 18, 19, 22, 23, 24.
The following are exceptions to the responses:
• If UF4 is received with RR of 16 through 31 the unit will respond with DF 20.
• If UF5 is received with RR of 16 through 31 the unit will respond with DF 21.
• If UF20 is received with RR of 0 through 15, the unit will respond with DF4.
• If UF21 is received with RR of 0 through 15, the unit will respond with DF5.
• If UF16 Broadcast interrogation is received, the unit will not reply. If UF16 non-Broadcast interrogation
is received, the unit will reply with DF16 if RL indicates a request for a long reply, otherwise it will reply
with DF0.
• IF UF0 is received with RL=1 the unit will respond with a DF16.
Note 2: The GTX 23 does not source the data for extended squitter / ADS-B messages. The GTX 23
must receive this data from other equipment in order to provide extended squitter / ADS-B functionality.
Also, ADS-B must be configured on.
Note 3: Compliance with elementary surveillance, enhanced surveillance, and extended squitter ADS-B
is shown at the installation-level per EASA CS-ACNS. The GTX 23 implements the technical
requirements necessary of a transponder that CS-ACNS requires, but installation of a GTX 23 by itself
does not constitute compliance with elementary surveillance, enhanced surveillance, or extended
squitter ADS-B requirements. Also, in order for the GTX 23 to meet the technical requirements of
CS-ACNS for enhanced surveillance or extended squitter ADS-B, the GTX 23 must have the feature
configured on and it must receive data to populate the relevant BDS registers.
25 Foot increments from -1000 to 50,175 feet with suitable serial
data altitude. 100 Foot increments from -1000 to 62,700 feet.
The Telecommunications Act of 1996, effective February 8, 1996, provides the FCC discretion to
eliminate radio station license requirements for aircraft and ships. The GTX 23 installation must comply
with current transmitter licensing requirements. To find out the specific details on whether a particular
installation is exempt from licensing, please visit the FCC web site http://wireless.fcc.gov/aviation.
If an aircraft license is required, make application for a license on FCC form 404, Application for Aircraft
Radio Station License. The FCC also has a fax-on-demand service to provide forms by fax. The GTX 23
owner accepts all responsibility for obtaining the proper licensing before using the GTX 23.
The UHF transmitter in this equipment is guaranteed to meet federal
communications commission acceptance over the operating temperature range.
Modifications not expressly approved by Garmin could invalidate the license and
make it unlawful to operate the equipment.
1.9 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. The article may be
installed only if performed under 14 CFR Part 43 or the applicable airworthiness requirements.
It is the installer’s responsibility to ensure the ADS-B Out system is compliant with AC 20-165 and to
ensure compatibility between the GTX 23 and the ADS-B Out position source equipment. See Garmin
ADS-B Out Compatible Equipment (190-01533-00) for compatible equipment shown to be eligible for
14 CFR 91.227-compliant installations in accordance with AC 20-165.
Air Traffic Control Radar
Beacon System/Mode
Select
(ATCRBS/MODE S)
Airborne Equipment
Extended Squitter
Automatic Dependent
Surveillance –
Broadcast (ADS-B) and
Traffic Information
Services – Broadcast
(TIS-B)
1. Complies with ICAO Annex 10, Amendment 77 Tables: 2-64, 2-80, 2-96 functionality only when the Enhanced Surveillance
function is enabled during configuration.
2. Complies with TSO-C166a/ETSO-C166a functionality only when the Extended Squitter function is enabled during
configuration.
3. Complies with TSO-C166b functionality only when the Extended Squitter function is enabled during configuration.