03-Mar-2011 11:44

How to check for a possible ISDN2e line fault

If your ISDN2e digital lines are playing up there are ways to check for the possible problems.

Unlike a standard analogue phone line you cannot simply plug in a normal telephone to test an ISDN2e digital line.
However there are a few things you can check yourself and hopefully your telephone provider will talk you through a few basic checks and will be equipped with the special ISDN2e test phones if an engineer needs to make a site-visit.

Normally the first sign of a problem may be that you are unable to make phone calls (no dial-tone or “busy” showing on the phone display)

Do you know how many lines you have on your telephone system? (You may have line ‘keys’ that show this).
Each ISDN2e line comes as a pair (called channels) so you will normally notice that Lines 1 & 2 are not working or Lines 3 & 4 etc.

If you take a look at your ISDN2e lines you will normally find small grey boxes near your PBX telephone system. Remember each ISDN2e line comes as a pair so if you have 4 phone lines (Lines 1-4) on your phone system, you should expect to find 2 of these grey boxes (called NTE8′s).

Look at the small LED in the middle of each box. If the LED is on (steady green) then the line should be working fine; if the LED is off there could be a disconnection between the local telephone exchange and your premises – contact your telephone line provider to report the fault and ask for a line test (you could also ask for a divert of your incoming calls to another number until the fault is fixed).

If the LED is ‘blinking green’ the fault could be on the telephone system or connecting cable, you should contact your phone system maintainer for further advice.

Please note that remote line tests and on-site LED checks are a guide only, and not an exact indication of the fault. Please be aware too that you may be charged for a callout if the BT phone system engineer visits and finds the fault is on your system rather than the lines.