BendixKing KXP 756 - Manual (Page 28)

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a remote mounted push button switch
to also activate the Ident reply.
When the Function Selector knob
is in the ON position, the transponder
replies to both Mode A and Mode C
interrogations but without flight level
information. With the Function
Selector knob in the ALT position, the
transponder automatically selects the
proper reply to either a Mode A or
Mode C interrogation transmitting
flight level information if an altitude
encoder is a part of the installation. An
optional switch permits the
transponder to reply Mode B
interrogations which are used in place
of Mode A interrogations in some
areas outside of the U.S.
An automatic dimming function
adjusts the brightness of the displayed
data and nomenclature to compensate
for changes in the ambient light level.
A provision is made in the KFS 576A
to cause the display to respond with
maximum brilliance if needed, by an
external switch.
The test position of the Function
Selector knob provides for a preflight
or airborne check of transponder
operation. This check will be
independent of any ground
interrogation. Switching the Function
Selector knob to the Test position
should cause the R (reply indicator) to
flash or illuminate continuously. If an
altitude encoder is a part of the
installation, the flight level input to the
transponder and the letters FL will
also be displayed. The flight level
readout is displayed in 100 foot
increments, thus a readout of 005
indicates 500 feet, or a readout of 042
indicates a flight level of 4200 feet. If
an encoder is not included in the
installation, a reading of -002 hundred
feet will be displayed, unless the
control unit is a KFS 576 Mod 1 or a
KFS 576A then dashes will appear.
The transmitter is inhibited during the
test function. The TST position
provides a momentary test function in
the KFS 576A and after 3 seconds the
unit will revert to the “ALT” mode.
In a dual system with KFS 576
Mod 1 or KFS 576A control unit, the
external standby function may be
used. If the system is configured in
this manner, the active transponder
will function as normal. The inactive
(external standby) transponder will not
transmit regardless of the position of
the function switch. In any functioning
mode except test, display will show
the reply code of the standby unit. The
letters SBY will indicate that the unit is
in standby mode. The unit that is in
external standby will show the flight
level when the function switch is
placed in the test position and the
letters FL will illuminate. The KFS
576A provides only two modes with
the function switch, clockwise for flight
level information and counterclockwise
for the standby aircraft identification
code.
Note: The flight level readout is not
corrected for atmospheric pressure
changes.
A maintenance check of the
transponder system and/or altitude
encoder should be performed if the
system fails the self-test function.