Dialling out puts extra voltage on the line and 'makes' the poor connection that was 'breaking' at lower volts?
A FWIW; That was the ISP engineer's best guess on Tuesday and since then we've discovered a "legacy"
connection buried in render on an external wall that was getting nicely soaked by the record rainfall we've beeen experiencing "chez nous". Line engineer came out earlier today and installed a completely new line from the roadside pole to the first socket in the house and despite the fact it is now seriously hissing it down the connection is solid....that said the next 24 hours will be a real test of the line and connections.
[ MétéoFrance ]
Thanks again for all the advice - if you don't hear from me again you'll know the new line failed it's first test..
