If you're having problems with your ADSL/VDSL broadband or phone connection, it's important to try an isolation test. Devices plugged into your jack points can interfere with your broadband, and an isolation test checks whether things such as the internal wiring of your house, a faulty ADSL filter, or another device is causing your problems.

How to do an isolation test

1. Disconnect all equipment plugged into your jack points e.g. double adapters, phones, filters, extension cords, fax machines, modems, Sky TV etc.
2. Wait for at least 30 seconds.
3. Plug the modem back in, without a filter, and wait for it to reconnect. If the lights labelled 'ADSL Sync' (sometimes labelled 'ADSL', 'Sync', 'WAN' or 'Broadband') and 'Internet' (sometimes labelled 'Online') light up, then your modem has reconnected.
4. If your modem reconnects, check to see if the problem you were experiencing is resolved. If it is, this means that one of the devices you unplugged was causing interference on your phone line. Plug your equipment back in one by one, checking the connection each time. When the problem returns, you have discovered the faulty device. Keep testing the rest of your equipment as well, as it could be more than one faulty device.
5. If your modem doesn't reconnect, the problem may lie with your jack point or phone cable. Try a different cable, and if that doesn't work, try the other jack points in your house, still checking the connection each time.

If you discover a piece of faulty equipment, it will either need to be replaced or you may simply require a new ADSL/VDSL filter.

If the test so far hasn't located the problem, try checking the following equipment too:

Modem: The best way to test your modem is to take it to someone else's place and plug it in there. This will confirm whether or not the problem lies with the modem. If you have tried all the jack points in your home with no success, but your modem works elsewhere, then you may have a wiring issue. Please contact us.

Filter: Try another filter or connect the phone or modem directly to the jack point to see if it makes a difference. (Filters should not be used for customers on the Genius plans as only your modem should be plugged into the jack points, nothing else.)

Third-party devices: If you have a device connected in between your modem and computer, remove this and connect the computer directly to the modem.

Computer: If you do have another computer, connect it directly to your modem via the LAN/Ethernet cable and see if it makes a difference.