ZyXEL Communications P-793H v3 User Manual page 231

The following table describes the fields in this screen.
Table 109 Maintenance > Diagnostic > DSL Line
LABEL DESCRIPTION
DSL Line Status Click this to view statistics about the DSL connections.
noise margin downstream is the signal to noise ratio for the downstream part
of the connection (coming into the P-79X from the ISP). It is measured in decibels.
The higher the number the more signal and less noise there is.
output power upstream is the amount of power (in decibels) that the P-79X is
using to transmit to the ISP.
attenuation downstream is the reduction in amplitude (in decibels) of the DSL
signal coming into the P-79X 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.
Chapter 24 Diagnostic
P-79X Series User's Guide
231