44
Each code comprises one or rnore
of
the 12
pulses
of
information
located between the so-calied frame
pulses
Fl
and
F2. ln the centre between the
information
pulses, a pulse
gap
exists, the pulse location
provided
for
this
gap always remaining vacant. A special
identification
pulse
is
the
SPI
pulse which
sends
for
approx.
20
seconds by the transponder, triggered by the
pilot
only
special request
of
the ATC. This
is
done
by the
pilot
briefly
pressing the
IDENT
button.
The
12
information
pulses
are
divided
into
four
groups
of
three pulses each,
the
four
groups
are
identified
A,
8,
C and D (in accordance
with
the 1st
to
4th
digits
of
the code readout).
Each
pulse
within
a group
also carries a
number
(1, 2
or
4). The coding n\Jmber belonging w one
of
the groups
of
letters
is
the
sum
of
the ·rndividual numbers
of
this group,
e.g.
the code number 5
in
Qroup A produces pulses A 1 and A4.
The
following
table shows
how
ali
code numbers
with
in the
four
groups
are
related.
Code
Impulse group
setting
first number
second
number
third
number
fourth number
A group
B group
C
group
D group
0
- -
-
-
1
A1
81
C1
Dl
2
A2
82
C2
02
3
A1,
A2
81'
82
C1,
C2
01'
02
4
A4
84
C4
04
5
A1,A4
81'
84
C1, C4
D1,
04
6
A2,A4
82,84
C2,C4
D2,D4
7
A1,A2,A4
81,82,84
C1, C2, C4
01,02,04
1 n
the
following
example the configuration
of
the coded
2134
is
shown on the
bas;s
of
the
coded pulse
sequence.
F1
C1
C2
A2
81
Dl. F2
Coding,
e.g.
2134
ln a mode C response, the
same
code system
is
used
at the 12
information
pulses providing
information
as
to
the height
of
the aircraft. Coding
is
provided
by
an
encoding
altimeter
connected
to
the transponder.
09/80
<t
0
ci
00
00
>
0
The document reference is online, please check the correspondence between the online documentation and the printed version.
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