Transponder Mode Selector
STBY (Standby) – Does not transmit.
ALT RPTG OFF(Altitude reporting off) – Transponder operates
without altitude reporting.
XPNDR – Transponder operates with altitude reporting.
TA ONLY(Traffic advisory) - Enables TCAS traffic warnings.
TA/RA (Traffic advisory / Resolution advisory) – Enables TCAS
traffic warnings and resolution advisories.
TEST (Push) – Starts ATC transponder functional test.