This seemed like a common problem at first:
Customer purchased a new cordless phone, plugged it in, and now, whenever the phone rings (or a call is made), his ADSL internet connection drops out for a few minutes.
In most cases this just means the new phone is connected to a new outlet that doesn’t have an ADSL filter connected.
So I go to plug in a line filter, but find that the phone doesn’t work… no dial tone, nothing.
Next step is to try a normal “corded” phone… these are getting rare nowadays…
Well, I get the same problem… no dial tone… the phone line is dead.
So I ask: have you ever used a phone on this outlet before (I’m starting to think that the phone plug either goes nowhere, or it was for a second phone line).
But the customer is sure it was used for a phone a few years ago.
OK, maybe some corrosion on the contacts… this is one of those old-fashioned Australian plugs from 20 or 40 years ago… about 1 inch square.
So I insert and remove the plug about 5 times… and the phone now has a faint dial tone… but the line quality is very noisy.
I try another 5 “in and outs” to remove some more corrosion, and the phone line now sound good.
Now I plugin the filter and the phone goes dead again… hmmm, maybe a faulty filter… some filters are more problematic than others…
I try a different filter, and the phone is now working again.
I now plugin the cordless phone, and it too is working.
Next, I make a call while watching the ADSL modem, and it maintains an internet connection while I call.
All fixed! (but with a few minor hiccups along the way!).