Skip to content

Performing an isolation test

What’s an isolation test?

Issues with your internet connection are often caused by devices or equipment connected to your phone line and could be the result of faulty filter/splitters, broken Ethernet cables, landline telephones, fax machines or even digital set-top boxes causing inference.

If you’re experiencing slower than usual speeds, internet dropouts or static noises on your phone line, conducting this test can help isolate any equipment in your home that might be interfering with your network connection.

Check for an outage in your area

nbn™ service

To find out if planned maintenance or an outage is affecting your nbn™ service, use the nbn network outages checker.


To find out if planned maintenance or an outage is affecting your ADSL service, we suggest using Down Detector or call us on .

If there’s no outage, continue with the test below.

To perform an isolation test:

  1. Remove all your devices and equipment (filters/splitters/Ethernet cables) from your phone line and modem. This includes, not just the phone socket you connect your ADSL through, but all phone lines on your premises.

  2. Next, connect your modem directly to your phone socket using the phone cable.

  3. After you’ve done that, connect your computer directly to your modem.

  4. Using your computer, check to see if your internet connection has improved. If that’s the case, it’s highly likely that one of your devices or a faulty filter is the cause of your internet connection problem.

  5. To find out which of your devices or equipment is faulty, start by plugging them back in, one by one—checking each time, to see if it’s affected your internet connection or the speed. If your internet connection appears faulty, it is most likely the device or piece of equipment you’ve just plugged back in.

  6. Once you’ve identified the faulty equipment or device, you’ll need to replace it.

  7. If you still can’t identify the problem, it might be the phone socket you’re using. Try connecting to another socket.

If you’ve run the test and you’re still not able to identify and resolve the problem, call us on and we’ll look into it for you.

If you’re not already logged in, you’ll be directed to log in to your Belong account before proceeding.

Was this article helpful?

Still need help? Let’s talk

Call us on or go to the “Let’s chat” button at the bottom of your screen between 8am and 8pm (AEST), 7 days a week.