It answers for a second and then disconnects the...

Question

It's set on fax only. I've had this machine for over a year and never had a problem. When calling in, it rings for 1/2 ring and then disconnects the call. It doesn't matter if it's another fax machine calling or another phone. It is a seperate line used just for the fax machine. There is a dial tone when I pick up the receiver,and I don't know what's wrong. I looked through the manual and it doesn't cover this problem. All of the setting look fine. Help........