Fax error the line is busy

XP Pro. Modem works fine to connect to AOL. I can send a fax to a local
number. Diagnostics show successful at end.

When I try to send a fax to an outside area code, I get repeating message
the line is busy. This for several fax numbers I've tried and all of which
when I dial manually give me the high pitch, indicating they're ready to
receive.

I have dialing set up to dial a 1 for an outside line. It looks like FAX
has the right number; it shows the +1 & area/number. It should work, but
it's not.

Any ideas?

Regards, Ron