Garmin G3X Installation Manual page 314

23.4.6 Mode Selections, GDU System ID Program Pins
In a single-display system, configure the display as PFD1. In a system with multiple displays, one display
must be configured as PFD1, and the other displays may be configured using any of the following
combinations:
• Single-display system: PFD1
• Two-display system: PFD1 + MFD1, or PFD1 + PFD2.
• Three-display system: PFD1 + MFD1 + PFD2, or PFD1 + MFD1 + MFD2.
• Four-display system: PFD1 + MFD1 + PFD2 + MFD2.
In a multi-display system, each display will automatically change to reversionary mode if certain other
displays are not detected:
• In all system configurations, PFD1 will change to reversionary mode if MFD1 is not detected, and
MFD1 will change to reversionary mode if PFD1 is not detected.
• In a three-display system with two PFDs and a single MFD, PFD2 will change to reversionary
mode if MFD1 is not detected.
• In a three-display system with a single PFD and two MFDs, MFD2 will change to reversionary
mode if PFD1 is not detected.
• In a four-display system, PFD2 will change to reversionary mode if MFD2 is not detected, and
MFD2 will change to reversionary mode if PFD2 is not detected.
A GDU 4XX can also be manually placed in reversionary mode by wiring Pin 25 to a two pole switch that
toggles between open and ground. When the switch is open, the display will operate normally. When the
switch is grounded, the display changes to reversionary mode. Other displays in the system will not be
affected by manually placing a display into reversionary mode. See the G3X Touch Pilot's Guide for
further information about reversionary mode.
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G3X/G3X Touch Installation Manual - LRU Pinouts
Page 23-23