ZyXEL Communications P-661H-61, Manual

Page: 264 / 404

Chapter 25 Diagnostic
P-661HNU-Fx User’s Guide
264
DSL Line
Status Click this button to view statistics about the DSL connections.
1. noise margin downstream is the signal to noise ratio for the
downstream part of the connection (coming into the ZyXEL Device from
the ISP). It is measured in decibels. The higher the number the more
signal and less noise there is.
2. output power upstream is the amount of power (in decibels) that the
ZyXEL Device is using to transmit to the ISP.
3. attenuation downstream is the reduction in amplitude (in decibels) of
the DSL signal coming into the ZyXEL Device from the ISP.
Discrete Multi-Tone (DMT) modulation divides up a line’s bandwidth into sub-
carriers (sub-channels) of 4.3125 KHz each called tones. The rest of the
display is the line’s bit allocation. This is displayed as the number (in
hexadecimal format) of bits transmitted for each tone. This can be used to
determine the quality of the connection, whether a given sub-carrier loop has
sufficient margins to support certain ADSL transmission rates, and possibly
to determine whether particular specific types of interference or line
attenuation exist. Refer to the ITU-T G.992.1 recommendation for more
information on DMT.
The better (or shorter) the line, the higher the number of bits transmitted for
a DMT tone. The maximum number of bits that can be transmitted per DMT
tone is 15. There will be some tones without any bits as there has to be
space between the upstream and downstream channels.
Reset
ADSL Line Click this button to reinitialize the ADSL line. The large text box above then
displays the progress and results of this operation, for example:
"Start to reset ADSL
Loading ADSL modem F/W...
Reset ADSL Line Successfully!"
Table 81 Maintenance > Diagnostic > DSL Line
ITEM DESCRIPTION