Isolation Test

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What does the Isolation test do?

The Isolation test checks for electrical interference caused by the telephony devices.

How do I run the Isolation test

Please follow these steps to perform an isolation test.

First remove ALL devices that are connected to the telephone line used by your ADSL modem. The reason this is asked, is to try and eliminate any hardware issues at this stage at your premises that may be interfering with your ADSL line sync/speed You should do this systematically using the following check list:

Tick.png Power off your ADSL modem and unplug all cables.

Tick.png Unplug all telephone handsets and cordless phones, remembering the extension in the garage, bedroom etc.

Tick.png Unplug all fax machines

Tick.png Remove all ADSL filters

Tick.png Remove all telephone double adapters/splitters

Tick.png Remove all telephone extension cables

Tick.png Unplug Foxtel/Austar Digital TV connection to the phone line

Tick.png Unplug any building alarm. If unable to unplug the telephone line from the alarm, then power off the alarm unit.

When you are certain that all devices that use the telephone line at your premises have been unplugged, proceed to the next step.


  • Plug a short telephone cable (RJ11), preferably less than 2 meters in length, into the Telephone, DSL or Line port at the back of your ADSL modem, and then plug the other end of the cable (RJ11) directly into your telephone socket. Check that the telephone cable is firmly plugged in and not damaged.
  • Plug your ADSL modem's power supply into a power outlet, but do not turn the power on yet.

DO NOT place an ADSL filter between the modem and the telephone point on the wall.

  • Plug your Ethernet (RJ45) cabling into the back on the modem, and then into the back of your computer.


Turn the power to your modem on, from the power outlet.

Identify the light on the modem that tells you when your modem is connected to the ADSL service. Sometimes this is called LINK, LNK, SYNC, DSL or WAN, depending on the modem type. In most cases the light will be steady and not flashing when it is connected

If the light is solid and not flashing at this point, then there is a physical link to the exchange.

Plug in each of the devices you unplugged in the first step, ensuring that you have correctly installed an ADSL filter on the telephone line between the device and the telephone wall socket.

Check the light on the ADSL modem that indicates you have a connection after you plug in each device. If the light starts flashing after you plug in a device this indicates the device or filter is faulty. Check that the filter is correctly installed (please see the Hardware Installation Guide to confirm). Replace with another filter.

Repeat this procedure for all telephones, faxes, digital TV, building alarms, remembering to install the filter and check the ADSL modem after adding each device.

Repeat the procedure for all telephone double adapters/splitters and telephone extension cables installed, checking the ADSL modem after each installation.