Garmin GPS 155XL Installation Manual page 35

4.4.5 Communications Loopback Test
This page displays the results of communication loopback tests. Three channels are tested: RS232
channels 1 and 2, and ARINC 429. Results of the test are either "OPEN" or "OK." Open means the
channel's transmitter and receiver are not connected or the test failed. The tests are performed
continuously while on this page except for RS232 channel 2 (this channel is only tested at power on and
the results are displayed on this page). Therefore, the unit must be turned off and the receiver/transmitter
connected or disconnected. Then turn the unit on to perform the test.
Use the following settings to test the channels:
•
RS232 channel 1—Connect RS232 channel 1 receiver and transmitter
•
RS232 channel 2—Connect RS232 channel 2 receiver and transmitter
•
ARINC 429—Connect ARINC 429 receiver and transmitter
4.4.6 Altitude Input Test
Select the Gray Code Altitude Test Page if this input is used. Verify that the altitude input is reading the
correct altitude, note that this page does not display serial altitude.
4.4.7 OBI Test
Select the OBI Test Page. Using the controls on the GPS 155XL/GNC 300XL front panel, make the
selections indicated below and verify the interfaces as appropriate:
OBI Data
Setting
VALID
INVALID
OBI Value—Ensure that the OBI displays the value entered when the VALID option is selected
The 3 lines that make up the OBI interface may be toggled individually. This may be done from
the "Value" field. Cycle this field to the desired line (either CLOCK, DATA, or SYNC) and
toggle the output to HIGH or LOW.
4.4.8 Signal Acquisition Test
Following normal power-up, the Self Test Page will be displayed followed by the Data Base Page. Upon
approval of the Data Base Page, the Satellite Status Page will be displayed. If the unit is unable to
acquire satellites, relocate the aircraft away from obstructions which might be shading reception. If the
situation does not improve, check the antenna installation.
Once GPS position information is available, use the DIRECT-TO key to activate the navigation function
to a nearby NAVAID, intersection, or airport. Ensure any connected equipment is transmitting data to
and/or is receiving data from the GPS 155XL/GNC 300XL and is functioning properly (see the Pilot's
Guide for more information on the DIRECT-TO function).
GPS 155XL/GNC 300XL Installation Manual
190-00067-22
Ensure that the OBI indicates the proper value
Ensure the OBI is invalid
NOTE
Test
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