Line Attenuation
20dB and below Outstanding
20dB-30dB. Excellent
30dB-40dB Very Good
40dB-50dB Good
50dB-60dB Poor and may experience connectivity issues
60dB and above Bad and will experience connectivity issues
SNR (Signal to Noise Ratio)
6dB or below Bad and will experience no line synchronisation or
intermittent synchronisation problems.
7dB-10dB. Fair but does not leave much room for variances in
11dB-20dB. Good with little or no synchronisation problems
20dB-28dB. Excellent
29dB Or above Outstanding

Note: SNR may be referred to as “Noise” or similar on some products, and where figures for both upstream and downstream are displayed all figures need to be taken into account.

See the Phoneworks ADSL Troubleshooting page for more information on these figures.

If you have a poor SNR figure (6 or less) the first thing to check is if the fault is on your premises. To find that out performa Line Isolation Test. If that makes no difference it’s most likely a fault on your telephone line in between your premises and the Telephone Exchange so consult your ISP*.

* ISPs are notoriously reluctant to organise a technician to check the line because it costs them money whether a fault is found or not so it may often take some negotiating to get the problem fixed. They may also recommend a change of profile (ie sacrifice some performance for stability) which is often an acceptable workaround.

Tip: If you’re still unsure whether a fault lies with your modem or with the ISP or the phone line, the only way to be sure is to try another modem or try your modem at another location that is known to be fine.