190-01499-02 GTX 3X5 Transponder TSO Installation ManualRev. 4 Page 5-7Table 5-5 Power Configuration and Power Control Functions5.4 Lighting BusThe lighting bus input controls the front panel display and keypad brightness of panel mount units usingthe aircraft panel lighting bus. The GTX 3X5 can also be configured to adjust the display and keypadbrightness for ambient lighting conditions using an internal photo sensor.The lighting bus input is configured for 5 VDC, 14 VDC, 28 VDC, or 5 VAC inputs.Use both the LIGHTING BUS HI and LIGHTING BUS LO inputs to connect the lighting bus input to a 5VAC bus.Use the LIGHTING BUS HI input to connect the light bus input to a DC input. The return is the unitground connection. LIGHTING BUS LO should be left open.Table 5-6 Lighting Bus Pins5.5 Altitude InputsThe GTX 3X5 uses pressure altitude inputs from several different sources:• Gray code inputs• RS-232 serial inputs• ARINC 429 inputs• The optional GAE module (Garmin P/N 011-03080-00)• HSDBRefer to section 3.10 for altitude source priorities.With the proper encoder, the Mode S transpondertransmits altitude reporting in 25-foot resolution to ground stations and other aircraft. The unit mustreceive altitude from an applicable altitude reporting device or from the optional GAE module. A parallelGray code encoder provides altitude in 100 foot resolution.For altitude encoders that supply both a serial interface and the parallel Gray code input, such as the GAE43 (P/N 013-00066-00), connect one or the other interfaces, but not both. The serial interface is preferred.5.5.1 Pressure Sensor ModuleThe optional GAE module (Garmin P/N 011-03080-00) is used for the GTX 3X5 pressure altitude input. Ituses the same interface as the configuration module and also includes the configuration modulefunctionality.POWERCONFIGPOWERCONTROL Unit Type DescriptionOpen Open Panel mount Auto on disabled, momentary power switch enabledOpen Ground Panel mount Auto on enabled, momentary power switch enabledGround Open Remote Power offGround Ground Remote Power onPin Name Connector Pin I/OLIGHTING BUS HI P3251 19 ILIGHTING BUS LO P3251 40 I
