Page 4-16
GTN 725/750 TSO Installation Manual
Rev. A
190-01007-02
4.3.7 Main
Indicator
4.3.7.1
Main Indicator Function
The Main Indicator displays both lateral and vertical deviation from selected course, To/From indications,
lateral and vertical flags and superflags.
The “CDI” button on the screen of the GTN takes the place of remote “NAV/GPS” switches, and is used
to toggle between display of GPS and VOR/ILS navigation on a remote indicator. The navigation source
is annunciated on the display below the ‘CDI’ button. The navigation method is optionally annunciated
externally by connecting to the VLOC ANNUNCIATE output (P1001-52) and GPS ANNUNCIATE
output (P1001-15). GPS and VOR/ILS navigation may be toggled externally when the CDI SOURCE
SELECT input (P1001-39) is momentarily grounded. See Section
TBD
and
TBD
for more information
on the discrete inputs and outputs.
An OBS resolver connection to the GPS is preferred, but not required. For the GTN 650 and GTN 750,
an OBS resolver typically is connected to the MAIN OBS inputs for use with the VOR receiver.
4.3.7.2
Main Indicator Electrical Characteristics
4.3.7.2.1 Deviation
Pin Name
Connector
Pin
I/O
MAIN LLEFT OUT
P1001
49
Out
MAIN LRIGHT OUT
P1001
68
Out
MAIN VEUP OUT
P1001
12
Out
MAIN VEDOWN OUT
P1001
31
Out
The deviation output is capable of driving up to three 1000
Ω
meter loads with
±
150 mVDC
±
10% for
full-scale deflection. The drive circuit provides for more than full-scale deflection with a maximum
course deviation output voltage of ±300 mVDC
±
10%.
4.3.7.2.2 TO/FROM
Pin Name
Connector
Pin
I/O
MAIN +TO OUT
P1001
11
Out
MAIN +FROM OUT
P1001
30
Out
The output is capable of driving up to three 200
Ω
meter loads. When indicating TO, MAIN +TO OUT is
+225 ±75 mV DC with respect to MAIN +FROM OUT. When indicating FROM, MAIN +TO OUT is -
225 ±75 mV DC with respect to MAIN +FROM OUT. When invalid information is present (Flag IN
VIEW) the TO/FROM output is 0 ±20 mV DC.
4.3.7.2.3 Flags
Pin Name
Connector
Pin
I/O
MAIN LFLAG OUT
P1001
50
Out
MAIN LATERAL -FLAG OUT
P1001
69
Out
MAIN VEFLAG OUT
P1001
51
Out
MAIN VERTICAL -FLAG OUT
P1001
70
Out
The Flag outputs are capable of driving up to three 1000
Ω
meter loads. When valid information is present
(Flag OUT OF VIEW) the Flag output is 375 ±80 mV DC. When invalid information is present (Flag IN
VIEW) the Flag output is 0 ±25 mV DC.
Summary of Contents for GTN 725
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