Garmin MODE S TRANSPONDER GTXTM 330 - Manual (Page 4)

The GTX 330 transponder is powered on by pressing the STBY, ALT or ON keys, or by a remote avionics master
switch (if applicable). After power on, a start-up page is displayed while the unit performs a self test. (See your
Garmin dealer for software upgrades.)
Mode Selection Keys
OFF  Powers off the GTX 330. Pressing STBY, ON or ALT
key powers on the transponder displaying the last active
identifi cation code.
STBY  Selects the standby mode. When in standby mode,
the transponder will not reply to any interrogations.
ON  Selects Mode A. In this mode, the transponder replies to interrogations, as
indicated by the Reply Symbol ( ). Replies do not include altitude information.
ALT  Selects Mode A and Mode C. In ALT mode, the transponder replies to identifi ca-
tion and altitude 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 will not include altitude information.
Any time the function ON or ALT is selected the transponder becomes an active part of
the Air Traffi c Control Radar Beacon System (ATCRBS). The transponder also responds to
interrogations from TCAS equipped aircraft.
Code Selection
Code selection is done with eight keys (0 – 7) providing 4,096 active identifi cation 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 fi rst 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 fi ve 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 Confi guration Mode.