Garmin G3X Touch Installation Manual page 600

Discrete Inputs
The GEA 24 and GSU 73 support up to four discrete inputs (DISCRETE 1 through 4) which can be
connected to a variety of external switches or voltage signals and used to generate system alerts or control
other system functions. For instance, a discrete input could be configured to generate an audible alert and
a CAS (Crew Alerting System) message on the PFD display when an external switch is closed.
To configure a discrete input, first select whether the input should be Active Low or Active High. An
Active High input will be considered active when the input voltage is above an upper threshold, and
inactive when the input voltage is below a lower threshold. An Active Low input will be considered active
when the input voltage is below a certain threshold, and inactive when the input voltage is above a certain
threshold, or if the input is floating (not connected). In general, most switch-type inputs that are either
open or connected to ground should be configured as Active Low. See
25.14.5.1 for the specific voltage levels used for discrete input sensing on the GEA 24 and GSU 73.
After a discrete input is configured for either Active Low or Active High, it is assigned to a specific
function. The following discrete input functions are supported:
• User-Defined Alert - Used to display a custom alert on the PFD when the discrete input is active.
Both the message text and the message color can be entered. A red alert will generate an audible
warning tone.
• Canopy Closed - Used with a switch that activates the input when the aircraft canopy is closed and
locked. A solid yellow CANOPY OPEN message will appear on the PFD if the Canopy Closed
input is not active. If engine power is increased or the aircraft is airborne, the CANOPY OPEN
message will flash red and an alert tone will sound.
• Door Closed - Same as Canopy Closed except alert text is DOOR OPEN.
• Gear Down - Used with a switch that activates the input when the aircraft's landing gear is down
and locked. When active, a solid green GEAR DOWN indication is displayed on the PFD. If
inactive, and the aircraft is at a low engine power setting and a low altitude, a red CHECK GEAR
alert message appears and a warning tone sounds continuously. When the aircraft's indicated
airspeed is greater than VFE, VLE, or VLO (whichever is lowest) the CHECK GEAR alert
message will not appear.
• Gear Up - Used with a switch that activates the discrete input when the aircraft's landing gear is
fully retracted. A Gear Up input should be used in conjunction with another discrete input that is
configured for the Gear Down function. If neither the Gear Up nor Gear Down inputs are active, a
190-01115-01 G3X/G3X Touch Installation Manual - GDU 37X Config and Post Install Checkout
Rev. AC
Section 25.5.9 and Section
Page 33-130