RRAS and "dark" analog phone line

Hi there all,

I've a client that we're trying to transition away from a linux file server to
an SBS 2003 server. One of the issues that we're currently has to do with a
"tie line" that they're using.

I'm not certain of the exact terminology for this, but basically the local
telco installed a point to point analog phone line over which they're
connecting using two regular analog modems. The thing is that the line has no
dial tone and no ring tone. The linux server's modem would check the line every
90 seconds for a "call", hang up, and try again. The remote workstation modem
was simply set to not wait for a dial tone and to dial a comma (pause).

How can I emulate this with SBS? If I configure RRAS in the standard fashion
the server's modem waits for a ring tone before picking up, which means it
never picks up the line.

The only thought that I've had on this matter would be to reconfigure the modem
with a customised AT command string, but is there another way to do this?

Thanks for your consideration,
Justin