Garmin GTN 725 Cockpit Reference Manual page 20

Transponder Page (GDL 88 Installations with Mode C Transponder)
Standby Touch to place transponder in Standby mode. It is still
powered, but will not transmit information. STBY displays in
the squawk code field.
Ground Touch to place transponder in Ground mode. Mode S
interrogations will be allowed. GND displays in the squawk
code field.
On Touch to turn transponder On for Mode A operation. Will
transmit the squawk code when interrogated. ON displays in
the squawk code field.
Altitude
Touch for Mode C operation. The transponder will be on and
will transmit its squawk code and altitude when interrogated.
Reporting
ALT displays in the squawk code field.
VFR Touch to set the squawk code to 1200.
Anonymous Touch to arm anonymous mode.
Flight ID This field is active in GDL 88 installations that have
transponders.
NOTE: More detailed descriptions of the transponder panels for
all installations can be found in the GTN 725/750 Pilot's Guide,
P/N 190-01007-03.
12
GTN 725/750 Cockpit Reference Guide (CRG)
Touch to arm the
anonymous key.
Touch to enter flight
ID
190-01007-04 Rev. D