ZyXEL Communications P660HN-Fx User Manual

 Chapter 25 Diagnostic

ADSL Series User’s Guide

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!"

Maintenance > Diagnostic > DSL Line