ADSL Wiring and Troubleshooting Guide

Technical and Reference >> ADSL Wiring and Troubleshooting Guide

An ADSL line filter is required on each device plugged into a phone line, other than the ADSL modem itself.

With an ADSL modem plugged into the same phone outlet as another device

Without an ADSL modem plugged into the same outlet

ADSL Troubleshooting Guide

There are a number of factors which can affect the speed and stability of your ADSL connection. They can be broadly grouped into line quality, line length and the use of filters.

Line quality

Since the copper lines leading from the exchange to your house are often old and therefore deteriorating, you may have issues with your connection. Unfortunately there is not much that you can do about this, in some instances Telstra may install a new line for you, however this is quite expensive.

Line length

Line length plays a large factor in determining the maximum speed of your connection (and indeed if you can get a connection at all). Apart from living in a house close to your exchange, there is nothing you can do about the distance between your exchange and your house. That said, once the line is in your house, you should aim to have the shortest lead possible between your wall outlet and your ADSL modem. We recommend a maximum lead length of 3 metres. Anything over this can cause additional interference to be present. If it is necessary to have a longer lead, we recommend having a short lead between your telephone wall socket and ADSL modem, and extending the lead between your ADSL modem and your computer.
Please note that the ADSL phone line should be kept away from mains power lines where possible as these lines can induce interference into the ADSL connection.


An appropriate filter must be installed correctly on every phone device connected to your telephone line (minus the ADSL modem itself). The diagrams above show how to do this using our ADSL1 model, however the procedure is similar for our other models as well.
If you have more than 3-4 devices connected to your phone line (fax machines, telephones, back-to-base alarms etc), you should have a central filter (such as our ADSL6) installed by a licensed cabler.

If your connection is still slow or unstable, your first contact should be your ISP (Internet Service Provider).