Line Testing

Recently I had noisy phone line but adsl ok, then lost phone and adsl. Phoned BT on mobile, BT Assistance in India tested line and said no fault found would have to send BT to house and find internal fault charging £90. BT Open Reach most efficiently tested from junction box outside house and found a one wire bad connection 20 yards from house in a junction box.Repaired and all now OK again except download speed dropped from 16Mbps to 8Mbps.

My question is: how can a person in India test my line? and if he did, then how could he have got it so wrong?

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The testing is using an automated tester within the main telephony switch. I performs several tests, one of which uses a Time Domain Reflectometer - simplistically a pulse is sent down the line and when it find a termination or damage it is partially reflected back, the time is measured and converted to distance and will give an approximate location of the fault. The estimated distance may have suggested it was within your property or close by - and the "It might cost" warning ensures you are aware that if the fault is on your side then you know a bill could be sent.

In reply to a post by MHC:

The estimated distance may have suggested it was within your property or close by

The absolute margin for error will be large when the echo sounding is sent all the way from Asia!

In reply to a post by XRaySpeX:

In reply to a post by MHC:

The estimated distance may have suggested it was within your property or close by

The absolute margin for error will be large when the echo sounding is sent all the way from Asia!

Like he says 'from the main telephony switch'. Its the local exchange the test is run from.

You can run the same test yourself via the internet.

I had problem with my line. The ran a new cable from house to pole, pole to cabinet and then cabinet to exchange and they still do not know what caused the problem.

- did you miss it?

Thanks MHC that explains it well to me. I didn't realise that a tester in my local exchange could be remotely operated.

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I didn't realise that a tester in my local exchange could be remotely operated.

Remote testing has been available for many years, and now there are even more options, LLU lines can be tested also as they pass through TAMs in the exchange, also SDSL services and the like.

A simple call from a mobile can initiate a wide range of different tests and conditions to test against.