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Ericsson DIALOG - Dialog Telephone Transmission Performance

Ericsson DIALOG
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SENDING
dB
rel.
1 V per ry'm
1
(6(JQ
ohms
load)
-10
0-1000
Oh
Im
Line
resistorce
'"'\ /
I
'
-20
0.02
0,05
0.1
0.2
0.5
Fig.
35
24
5.
TRANSMISSION PROPERTIES
After
studying
that
part
of
the
instrument
diagram
directly
concerned
with
transmission
regulation,
we
must
turn
to
the
remaining
transmission
properties
of
the
instrument.
These
properties
are
of
course
to
a
great
extent
dependent
on
the
trans-
mission
regulation.
The
curves
referred
to
relate
to
the
instrument
connected
to a
feeding
system
of 48 V
with
2 x 250 Ohm
feeding
coils.
Fig.
35
shows
the
response
curve
during
sending
with
600 Ohm
termination.
The
shape
of
the
curve
applies
independently
of
the
line
resistance
up
to
1 000 Ohm.
As
can
be
seen
the
level
is
good
and
the
curve
even,
without
resonances.
The
curve
rises
with
frequency
for
compensation
of
the
cable
attenuation,
which
increases
with
the
frequency.
RECEIVING
dB
rel.
1 Njm
2
per V
emf
(600
ohms)
Artificia
ear as
perCC
TT
+20
lCOO
Ohn
~
Line
~
-
resistance
+10
0
Ohm
Lie
......
-\
re
istono
10
20
0.0
2
0,0
5
0.1
0.2
0.5
10
20
kHz
kHz
Fig.
36
Fig.
36
shows
response
curves
during
receiving
with
two
different
line
resistances
and
the
instrument
loaded
with 600 Ohm. The
curve
has
a good
level
and
a
flat
response.
The
highest
level
in
this
diagram
shows
the
curve
for
1 000
Ohm
line
resistance.
This
agrees
with
what
has
already
been
said
about
the
design
of
the
instrument.
With a
reduction
in
the
line
resistance
the
level
falls
owing
to
the
automatic
transmission
level
regulation.
and
its
lowest
value
is
at
0 Ohm
line.
The
results
of
the
curves
already
discussed
are
confirmed
by
the
reference
equivalent
curves,
which
will now
be
dealt
with.
First,
however,
a few
conditions
applying
in
general
for
these
curves
will
be
mentioned.
The
representative
frequency
for
which
the
cable
attenuation
is
added,
varies
with
the
cable
diameter.
Cable
attenuation
for
the
different
cable
dimensions
according
to
the
latest
proposal
by
CCITT
are:
0.4
mm
cable:
0.5
mm
cable:
0.6
mm
cable:
1.62
dB/km
1.22
dB/km
0.95
dB/km
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