I've run a test on your line and no fault has been found after automated testing

[#1]

Hi,
What exactly do these "automated testing" test?
Dan.

[#2]

It test the condition of the copper.  Inside the master socket is a 470K ohm test resistor which provide a close loop for testing impedance of the line.

[#3]

Thanks,
do you know what the  tolerance is given to this 470K ohm resistance? My phone line is long with a few joints, it is very likely that each joint could add more to the overall figure, part of my line between the cab and my house uses aluminum, copper to ali joints are prone to corrosion.
The strange thing is before they did the line test I had crackling on the line now it's gone! I expect the crackling will to do a Arnie! (I'll be back)
Dan.

[#4]

The tolerance on the resistor isn't really relevant as it's in series with the "ring/bell" capacitor. It's primary purpose is to allow some tests to be completed if you don't have a phone plugged in. When phones are plugged in, their bell circuits are connected across this resistor and the impedance can be somewhat lower than the resistor value.
The problem with "bad" joints is that they can and often are intermittent. Ringing current on the line can very often "clean" a joint temporarily, so the crackling will disappear for a while. Unfortunately one has to be persistent and a bit OCD with faults of this type, ideally report them whilst the line is crackly so the call taker can confirm they can hear the noise, and always report the problem as Intermittent and ask for that to be logged. Confirm that you've carried out checks in the test socket (or master if you don't have an NTE5a socket) to rule out any problems with internal wiring or sockets.