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400 SERIES MAINTENANCE MANUAL Page 1-1
P/N 190-00140-05 Rev. C
SECTION 1
DESCRIPTION AND OPERATION
1.1 INTRODUCTION
References made to the GNS 430 and the GNC 420 throughout
this manual equally apply to the GNS 430A and the GNC 420A
except where specifically noted.
This manual provides board-level maintenance information for the GARMIN 400 Series of
products. Table 1-1 shows each unit in the 400 series and their configurations. The system allows
the Main Processor software to recognize which of the optional components (VHF
Communications Transceiver, VOR/LOC receivers, and Glideslope receiver) are present.
Table 1-1. Unit Configuration
GPS 400 GNC 420 GNS 430
Main Processor
GPS Receiver
VHF Com Transceiver
VOR/ILS Localizer Receivers
ILS Glideslope Receiver
1.1.1 Versions Covered by this Manual
This manual applies to the GPS 400, GNC 420, and the GNS 430. It also applies to the
GNC 420A and the GNS 430A. The “A” identifies the 16 watt VHF COM transmitter as opposed
to the 10 watt version. Appendix A describes the GNC 420A and the GNS 430A. For ease of
identification, the following tables contain part number information relative to the different
versions of the 400 Series: