190-01115-01 G3X™/G3X Touch™ Avionics Installation Manual
Rev. AV Page 30-212
30.4.32.26 Discrete Inputs
Discrete inputs 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. Discrete inputs can also be used to trigger certain specific actions, as described below.
The GEA 24 and GSU 73 support up to four dedicated discrete inputs (Discrete 1 through 4). The GAD 27
supports an additional nine discrete inputs The seven general purpose (GP) inputs and the RPM2 input on
the GEA 24 may also be configured as additional discrete inputs.
NOTE
The GEA 24 GP 6 and GP 7 inputs require the LO side of the input to be connected to
ground. See Figure 26-2.2
for wiring details.
If two EIS LRUs are configured, the four discrete inputs on EIS LRU #2 may be separately configured,
providing four additional discrete input possibilities. The GP inputs on EIS LRU #2 are not available to be
used as additional discrete inputs.
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 Section 23.4.9
and Appendix F.5.5.1 for the specific voltage levels used for discrete input sensing on
the GEA 24 and GSU 73 (Section 23.1.6
).
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