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Isolation Test


When you have a single piece of equipment plugged into your phone line for testing purposes, it's called an isolation test. That single piece of equipment might be a modem if you're testing broadband, or a fixed (non-cordless) handset if you're testing your phone line.

Broadband modem isolation test

Isolation tests are most commonly performed when synchronisation has dropped out entirely, although they can also help when broadband is experiencing slow speeds.

  1. Start by unplugging everything you can around your premises from the phone line your broadband is connected to. This includes EFTPOS terminals, dialup modems, telephones, Foxtel Digital boxes, fax machines and anything else which uses the same telephone line as your broadband. If you have multiple telephone lines coming into your premises, you can leave any equipment on non-broadband lines plugged in.
  2. Once you've unplugged everything, connect your modem directly into the telephone wall sockets using a telephone cable no longer than a metre in length. Give it a few minutes to synchronise.
    • The modem does not need to be plugged into a computer at this point if you're testing a complete loss of synchronisation, but you should keep it plugged into your computer if you're testing speed problems.
  3. If the modem still hasn't synchronised after a few minutes, connect a telephone to that socket and make sure that the wall socket you're using has dial tone. Also you may wish to try alternative telephone sockets.

If synchronisation comes back

If the modem does synchronise, you can start plugging your telephone equipment back in. Give the modem around a minute after each device is plugged back in to see if the synchronisation light goes out. If it does, it's possible you've found a device which is interfering with your broadband.

If a piece of equipment is interfering with your broadband, it could be for any of the following reasons:

If synchronisation doesn't come back

If synchronisation doesn't come back during these tests, and your modem is definitely in good working order, it's possible your broadband service has stopped working altogether, in which case it's a good time to call our support line on 13 22 58 to report a possible fault. Don't forget to let them know what you've already tried.

Telephone line isolation test

You may be asked to perform a telephone line isolation test when your dial tone has dropped out completely.

  1. Start by unplugging everything you can around your premises from your phone line. This includes EFTPOS terminals, dialup modems, telephones, fax machines, Foxtel Digital boxes, broadband modems and anything else which uses your telephone line. If you have multiple telephone lines coming into your premises, you can leave any equipment on alternate lines plugged in.
  2. Leave everything unplugged for at least 10 minutes.
    • The reason you need to do this is because the exchange will protect itself from faulty equipment by switching your dial tone off. The exchange checks every ten minutes or so to see if the faulty equipment is still there, and if the problem's gone away it switches your dial tone back on.
  3. Connect a single telephone to one of your sockets with a short piece of cable, and check for a dial tone. If you don't get a dial tone, check on another telephone socket.

If the dial tone comes back

If you get your dial tone back, reconnect your telephone equipment to the line one piece at a time. Check for a dial tone after each piece of equipment is added. If at any point during plugging things back in you lose dial tone, it's very possible that what you just plugged in is the culprit. Check any suspect equipment at least twice to be sure it's not a coincidence.

If the dial tone doesn't come back

If you can't get a dial tone on any of your sockets, it's possible your telephone line is dead due to other causes. Before you call our contact centre on 13 22 58, try the following:

This information should assist us in getting your telephone service fixed more quickly.