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ADSL Isolation Test

If you seem to be experiencing issues with your broadband service then carrying out an ‘Isolation Test’ will allow you to narrow down where the issue may lie.  The following is particularly useful where slow speeds are concerned but can help alleviate issues with intermittent and no connection issues also.

First, locate the BT Master socket and remove the 2 screws to reveal the lower portion of the socket. If you do not have a socket like this then please do not continue as you will not be able to carry out the ‘Isolation Test’. BT have been installing NTE5 sockets since 1981 so there is a fair chance that you will indeed have a socket like the one pictured below and will be able to proceed with the test.


Please note that the master socket is the demarcation point between BT’s equipment and your own. Therefore you must not tamper with any equipment or cabling past the master socket.

The test socket within the ‘BT Master Socket’ is the point used by BT engineers to test for telephone and adsl faults. If an engineer is able to get a good signal from here then this points to the fault being on the customers side and therefore any engineer callout fees will be chargeable.

To test your adsl connection from this point either use an inline adsl filter or one of the cables that is normally used with a 56k modem. Please connect in a similiar fashion to the image below.


Once you have your ADSL router connected, please retest to determine if the issue you had previously has dissapeared. If the fault clears, during the isolation test, then it would appear to be due to a local issue and you will need to plug items in, one at a time, to narrow down where the problem lies. We would suggest that you start with the filter/telephone then one at a time any extensions/faxes etc. remembering that each must have a filter attached. Please note that Sky boxes are also required to be filtered.

If after carrying out the ‘Isolation Test’ you find that your issues have not been resolved, please call Pulsant on 08451199999 to report/progress your fault.