777 ATC Transponder & TCAS

Transponder Code Window
Displays the Code set by the Transponder Code selectors. Also displays the operating Transponder ( L or R ).

Transponder Code Selector
Sets the Transponder Code in the window and both transponders.

ABV / N / BLW Selectors
ABV
Displays altitude reporting traffic from 2700 feet below to 9900 feet above airplane altitude.
N (Normal)
Displays altitude reporting traffic from 2700 feet below to 2700 feet above airplane altitude.
BLW
Displays altitude reporting traffic from 9900 feet below to 2700 feet above airplane altitude.

ABS / REL Selectors
ABS
Target altitude information is displayed as three-digit absolute (indicated) altitude above sea level.
REL
Target altitude information is relative to present altitude )+/- two digits) or 00 for co-altitude.

ALT Source Selector
NORM
Selects the normal (ADIRU) altitude source for altitude reporting.
ALTN
Selects the normal (SAARU) altitude source for altitude reporting.

L/R Selector
Selects the left or Right transponder system.

IDENT, TCAS and XPNDR Selector
IDENT
Push to transmit an identification signal.
TCAS / XPNDR Selector
Rotate to:
STBY
TCAS and the transponders are in the standby mode.
ALT RPTG OFF
Transponder operates without altitude reporting and TCAS is in the standby mode.
XPNDR
Transponder operates with altitude reporting and TCAS is in the standby mode.
TA ONLY
The transponder is on. TCAS is on but only the Traffic Advisory function of TCAS is operational. Resolution Advisories and pitch guidance are inhibited. The message TA ONLY appears on the ND display.
TA / RA
The transponder is on and all Traffic Advisory and Resolution Advisory function of TCAS is operational. If a TA becomes active, the indications are the same as for TA only.