Page 5-14 GTN 625/635/650 TSO Installation ManualRev. C 190-01004-025.2.9 Discrete InputsPin Name Connector Pin I/OOBS MODE SELECT* P1001 16 InAUDIO INHIBIT IN* P1001 36 InTAWS INHIBIT IN* P1001 37 InAIR/GROUND* P1001 38 InCDI SOURCE SELECT* P1001 39 InDEMO MODE SELECT* P1002 1 InSYSTEM ID PROGRAM* P1002 10 InSPARE DISC IN D* P1002 11 InAn asterisk (*) following a signal name denotes that the signal is Active-Low, requiring a ground toactivate. If there is no asterisk, the signal is Active-High.Active-low discrete inputs are considered active if either the voltage to ground is ≤3.5 VDC or theresistance to ground is ≤375 . These inputs are considered inactive if the voltage to ground is6.5-33 VDC or the resistance to ground is >100 k .Active-high discrete inputs are considered active if either the voltage to ground is >6.5 VDC. Theseinputs are considered inactive if the voltage to ground is ≤3.5 VDC or the resistance to ground is≤375 .5.2.9.1 OBS MODE SELECT*The OBS MODE SELECT* discrete input may be used to toggle between GPS OBS and GPS AUTOmodes of operation. A momentary low on this pin performs the same function as pressing the ‗OBS‘ keyon the GTN display.5.2.9.2 AUDIO INHIBIT IN*The AUDIO INHIBIT IN* discrete input may be used to suppress TAWS and touch screen feedbackaudio from the GTN.5.2.9.3 TAWS INHIBIT IN*The TAWS INHIBIT IN* discrete input, when toggled momentarily low, may be used to inhibit TAWSalerts from the GTN.5.2.9.4 AIR/GROUND*AIR/GROUND* discrete is active-low, and can be configured to interpret if the aircraft is airborne or onthe ground based upon whether the input is grounded or open.5.2.9.5 CDI SOURCE SELECT* (GTN 650 Only)The CDI SOURCE SELECT* discrete input may be used to toggle between display of GPS andVOR/LOC/Glideslope information on the MAIN external CDI/HSI. A momentary low on this pinperforms the same function as pressing the ‗CDI‘ key on the GTN display.
