Installation Procedures2-4 560-0982-01 Rev L GNS 480 (CNX80) Installation Manual2.5.2 Existing SensorsWhen the GNS 480 is installed with external sensors, these sensors must be installed in accordance withthe manufacturer's data. This manual does not provide information for the installation of specific externalsensors.The GNS 480 can accept data from multiple altitude, heading, and baro correction sources. If multiplesources are used, the GNS 480 will accept data as described below.2.5.2.1 Multiple Altitude SourcesThe GNS 480 can accept altitude from an RS-232 altitude encoder, fuel/air data computer (FADC),ARINC 429 air data computer (ADC), an SL70/SL70R transponder, a GTX 33/330 transponder, andanother GNS 480.If multiple sources of altitude data are supplied to the GNS 480, only valid data from the highest prioritysource is used (input priority cannot be configured). If the highest priority source becomes unavailable,data is taken from the next-highest priority source. The priorities of the altitude sources are as follows(from highest to lowest):1. ARINC 429 ADC2. FADC3. RS-232 Altitude EncoderNOTEAlthough the GNS 480 can be configured to accept data from an RS-232 altitude encoderon different ports, the GNS 480 cannot accept data from two RS-232 altitude encoders.4. SL70/SL70R Transponder or GTX 33/330 Transponder that receives Gray code altitude.NOTEAltitude data received from a second GNS 480 will also be derived from one of the abovesources. Data received on the GNS 480 cross-talk input is treated as if it is receiveddirectly from the source that is supplying altitude to the second GNS 480. If the directinput and the GNS 480 cross-talk input have the same priority, data from the direct inputis used.NOTENot all models listed in Appendix C.2 are approved for use as an altitude source fortransponders. When configuring the GNS 480 to provide altitude data to a transponder,only devices approved in accordance with 14 CFR 91.217 may be used.2.5.2.2 Multiple Heading SourcesThe GNS 480 can accept heading from an ARINC 429 Heading Source, an FADC or an XYZ synchrosource. If multiple sources of heading data are supplied to the GNS 480, only valid data from the highestpriority source is used (input priority cannot be configured). If the highest priority source becomesunavailable, data is taken from the next-highest priority source. The priorities of the heading sources are asfollows (from highest to lowest):1. XYZ Synchro2. ARINC 429 Heading Source3. FADC