The house has a landline. When I plug the computer into the phone socket I can get online and connect to the internet. However I cannot get a dial tone on the telephones from the same socket (with the computer unplugged). Nor can I call the house landline number via a mobile, I hear a ringing tone on the mobile but the landline phone stays silent.

I have tried the helpdesk but they were numpties so I gave up.

I don't understand why the computer works but the phones don't? I have tried both cordless and an old cord phone.

Please help
Mxx
[/I]

Since it is ringing on Mobile, line is opening, not shorting.
Try unplugging computer, call your house, while it is ringing, plug in computer to see if it stops the ringing, I am suspecting the Jack itself. If DSL, do you have another filter to try?

Hmmm.. I wonder if there may be a fault with the telephone or the cord that connectes your phone to the jack? Have you tried that same phone in another jack? And are you plugging your phone directly into the outlet that your computer uses (i.e. no DSL filter in between)?

When you connect your computer to the phone line and connect, do you actually hear dial tone through the computer speakers and then the number for your ISP being dialed?