Argus 165, Руководство пользователя

Страница: 67 / 363

7 Operation on xDSL accesses
67
ARGUS 165
Displays the amplitude component of the
transmission function (HLOG) for each
tone. HLOG shows the attenuation of a
connection as a function of the frequency.

Y-axis: Hlog in dB

X-axis: tones (channels)
On a nominally functioning line, the values
drop off as the frequency increases; this
function is virtually horizontal on short
lines. This example shows a short line.
In the HLOG graphs, a shift can occur in
calculating the upstream and downstream
values from DSLAM compared to the
downstream values from ARGUS. It can
also happen that DSLAMs do not transmit
the HLOG upstream values or send
falsified values.
DSL connections are often possible even
though one of the two cores is high-ohm
or even interrupted (only capacitive
coupling). This results in dropped
connections and data losses. Such
problems can be due to oxidized lines,
poor contacts in the telephone sockets,
loose terminals or improperly insulated
lines. In connections like this, lower
frequencies are attenuated much more
than higher frequencies. This is
recognisable as an atypical relationship
between upstream and downstream
attenuation, as well as in the HLOG curve.
In the event of a problem on one of the
wires, the values for the low frequencies
are often less than for the higher
frequencies.
<Menu>
Opens the graph functions, see
page 62.
<Continue>
ARGUS returns to the bits/tone
graph.
Example: Mi poor contact

on ADSL