Theory Of Operation; Front Panel Assembly; Main Board; Waas Board - Garmin GTN 725 Maintenance Manual

3 THEORY OF OPERATION

3.1 Front Panel Assembly

The front panel assembly of the GTN 725/750 consists of the front panel and the touchscreen. The
GTN 725/750 navigators feature a 6.9" diagonal touchscreen which is used to perform most functions. The
front panel contains a data card slot, photocell, supplemental hard keys, volume control knob, and dual
concentric control knobs.

3.2 Main Board

The GTN 725/750 main board contains the main processor. The GTN 725/750 is capable of interfacing
with other aviation instruments through RS-232, ARINC 429, and Ethernet ports. The GTN 725/750 has a
main indicator function which displays both lateral and vertical deviation from selected course, to/from
indications, lateral and vertical flags and superflags with or without an OBS resolver connection. The
GTN 725/750 also supports configurable discrete inputs and outputs for annunciators, switches, and other
functions.

3.3 WAAS Board

The GTN 725/750 WAAS board contains the functionality of a GPS and Satellite-Based Augmentation
System (SBAS) satellite receiver.

3.4 I/O Board

The I/O board is an expansion board for the main board designed to add functionality to the GTN 750. The
I/O board supports discrete inputs and outputs, additional serial ports, and ARINC transceivers. The I/O
board also supports a synchro interface.

3.5 COM Board

The GTN 750 COM board contains the functionality of a VHF communications transceiver.

3.6 NAV Board

The GTN 750 NAV board contains the functionality of a VOR/LOC receiver and a glideslope receiver.
The GTN 750 NAV board also supports analog and ARINC 429 outputs.
190-01007-01 GTN 725/750 Maintenance Manual
Rev. 5 Page 3-1