Figure 2-4, Fms Controller; Figure 2-5, Transponder - Garmin G1000 System Maintenance Manual

2.1.5 GCU 477 FMS Control Unit
The GCU 477 functions as the primary control interface to the GDU 1500 MFD. The GCU 477 provides
alphanumeric, softkey, and flight planning function keys used to interface with the G1000; the MFD does
not possess any knobs or controls other than softkeys. The GCU 477 is powered by No. 3 Triple Fed
Bus. The GCU 477 also provides the crew with the added functionality of tuning their receivers via the
GCU as well as the PFD. Detailed instructions regarding the controls are discussed in the G1000 Cockpit
Reference Guide.
2.1.6 Transponder (2)
The Garmin GTX 33( ) or GTX 3000 transponders communicates with the on-side GIA 63W through RS-
232 digital interface. This STC installation allows for installation of two GTX 33 non-diversity
transponders, two GTX 33D diversity transponders, or one of each type. This STC installation also
allows for installation of two GTX 3000 diversity transponders. Mixing between the GTX 33 and GTX
3000 transponsders is not permissible. Additionally, for TCAS II operations, the GTX 3000 transponder
communicates with the GTS Processor through ARINC 429 digital interfaces (transmit and receive). The
transponder units are mounted on the upper avionics equipment shelf in the tail section of the airplane.
Power is provided by the No. 1 GTX from Triple Fed Avionics Bus. The No. 2 GTX is powered from
Left Gen Avionics Bus. All GTX transponders (non-diversity and diversity) interface with a transponder
antenna mounted to the bottom of the fuselage. Each diversity transponder (GTX33D and GTX 3000)
interfaces to a transponder antenna mounted to the top of the fuselage.
Page 2-4
Revision 4

Figure 2-4, FMS Controller

GTX 33()

Figure 2-5, Transponder

G1000 / GFC 700 System Maintenance Manual - 300/B300 Series King Air
GTX 3000
190-00716-01