Garmin GTX 330, GTXTM 330D TRANSPONDER INSTALLATION MANUAL
Brand: Garmin, Pages: 71
Page 31 from 71
GTX 330 Installation Manual Page 4-9
4.6.4 ARINC 429 Input/Output
The ARINC 429 Output 2 port, J3301 pins 30 and 28, is at a high-impedance when in remote standby,
therefore not active. When two GTX 330s are installed, the two ARINC 429 Output 2 ports may be hard
wired together since the EXTERNAL STANDBY SELECT input is active for only one of the two
GTX 330s at any given time.
The GTX 330 ARINC 429 Output 1 port is active when J3301 pin 13 is grounded [EXTERNAL
STANDBY SELECT (remote STANDBY)]. In installations having a transponder combination of
GTX 330/GTX 327 (or GTX 330/other transponder), the GARMIN and GARMIN W/TIS formats from
the ARINC 429 Output 1 port, J3301 pins 34 and 37, are available if the GTX 330 has SW 3.03 and
Table 4-9. ARINC 429 Pin Assignments
Pin Name Pin Number I/O
ARINC 429 OUT 1A 37 Out
ARINC 429 OUT 1B 34 Out
ARINC 429 IN 1A 32 In
ARINC 429 IN 1B 35 In
ARINC 429 IN 2A 33 In
ARINC 429 IN 2B 36 In
ARINC 429 OUT 2A 30 Out
ARINC 429 OUT 2B 28 Out
ARINC 429 IN 3A 26 In
ARINC 429 IN 3B 29 In
ARINC 429 IN 4A 48 In
ARINC 429 IN 4B 49 In
The ARINC 429 outputs conform to ARINC 429 electrical specifications when loaded with up to 5
standard ARINC 429 receivers. Refer to Figures C-1, C-5, C-6, C-7 and C-8 for the ARINC 429 serial
data interconnect and Sections 5.2.8 and 5.2.18 for ARINC 429 serial data configuration.
Page 32 from 71
Page 4-10 GTX 330 Installation Manual
This page intentionally left blank
Page 33 from 71
GTX 330 Installation Manual Page 5-1
5 POST INSTALLATION CONFIGURATION AND CHECKOUT
Perhaps the most important factor in the GTX 330 transponder configuration and checkout is the Mode S
address entry. Refer to Section 5.2.12 for Mode S address entry pages.
Be sure to check all aircraft control movements before flight is attempted
to insure that the wiring harness does not touch any moving part.
Verify proper operation of the transponder during a flight test under VFR conditions. If the unit detects
an internal failure mode the word FAIL is displayed on the screen.
Make sure an approved device is installed for reporting altitude in accordance with 14 CFR Part 91.217.
Refer to Section 4.4.4 for altimeter data selection priority.
The coverage you can expect from the GTX 330 is limited to line of sight. Low
altitude or antenna shielding by the aircraft itself may result in reduced range.
Range can be improved by climbing to a higher altitude. It may be possible to
minimize antenna shielding by locating the antenna where dead spots are only
noticed during abnormal flight attitudes.
Figure 5-1. GTX 330 Front Panel
The GTX 330 should be turned off before starting aircraft engine(s).
Page 34 from 71
Page 5-2 GTX 330 Installation Manual
5.1.1 Function Selector Switches
The function selection switches are:
• OFF Powers off the GTX 330. Pressing the STBY, ON or ALT key powers on the
transponder displaying the last active identification code.
• STBY Selects the standby mode. When in standby mode, the transponder does not reply
to any interrogations.
• ON Selects Mode A and Mode S. In this mode, the transponder replies to Mode A,
Mode C and Mode S interrogations, as indicated by the Reply Symbol (“
the replies do not include altitude information.
• ALT Selects Mode A, Mode C and Mode S. In ALT mode, the transponder replies to
identification, altitude and Mode S interrogations as indicated by the Reply Symbol
®”). Replies to altitude interrogations include the standard pressure altitude
received from an external altitude source, which is not adjusted for barometric
pressure. The ALT mode may be selected in aircraft not equipped with an optional
altitude encoder; however, the reply signal
does not include altitude information.
Any time the function switch is in the ON or ALT position the transponder
becomes an active part of the Air Traffic Control Radar Beacon System
(ATCRBS). The transponder also responds to interrogations from TCAS
• IDENT Pressing the IDENT key activates the Special Position Identification (SPI) Pulse
for 18 seconds, identifying the transponder return from others on an air traffic
controller’s screen. During the IDENT period the word ‘IDENT’ appears in the
upper left corner of the display.
• VFR Sets the transponder code to the pre-programmed VFR code selected in
Configuration Mode (Set to 1200 at the factory). Pressing the VFR key again
restores the previous identification code.
• FUNC Changes the page shown on the right side of the display. Display data includes
Pressure Altitude, Flight Time, Altitude Monitor, Count Up and Count Down
timers. In the Configuration Mode, steps through the function pages.
• START/ Starts and stops the Altitude Monitor, Count Up, Count Down and Flight timers.
STOP In configuration mode, steps through functions in reverse.
• CRSR Initiates entry of the starting time for the Count Down timer and cancels
transponder code entry. Selects changeable fields in Configuration Mode.
• CLR Resets the Count Up, Count Down and Flight timers. Cancels the previous
keypress during code selection and Count Down entry. Used in Configuration
Page 35 from 71
GTX 330 Installation Manual Page 5-3
• 8 Reduces Contrast and Display Brightness when the respective fields are displayed
and enters the number eight into the Count Down timer. Used in Configuration
• 9 Increases Contrast and Display Brightness when the respective fields are displayed
and enters the number nine into the Count Down timer. Used in Configuration
5.1.2 Code Selection
Code selection is done with eight keys (0 – 7) providing 4,096 active identification codes. Pushing one of
these keys begins the code selection sequence. The new code is not activated until the fourth digit is
entered. Pressing the CLR key moves the cursor back to the previous digit. Pressing the CLR key when
the cursor is on the first digit of the code, or pressing the CRSR key during code entry, removes the
cursor and cancels data entry, restoring the previous code. You may press the CLR key up to five
seconds after code entry is complete to return the cursor to the fourth digit. The numbers 8 and 9 are not
used for code entry, only for entering a Count Down time, contrast and display brightness, and data
selection in the Configuration Mode.
The selected identification code should be entered carefully, either one
assigned by air traffic control for IFR flight or an applicable VFR
• Important Codes:
1200 VFR code for any altitude in the US (Refer to ICAO standards elsewhere)
2000 VFR code commonly used in Europe (Refer to ICAO standards)
7000 VFR code commonly used in Europe (Refer to ICAO standards)
7500 Hijack code (Aircraft is subject to unlawful interference)
7600 Loss of communications
Avoid selecting code 7500 and all codes in the 7600-7777 range. These codes trigger special indicators
in automated facilities. An aircraft’s transponder code is used for ATC tracking purposes, therefore
exercise care when making routine code changes.