Phone and fax machine on the same line? With Faxability there's no confusion about where a call is heading. Your fax machine not only gets its own number – it also gets a special ringing pattern. So you know immediately who the call is for.
Your fax machine recognises the ring and immediately accepts the fax message. And you're not interrupting a fax's transmission because you think it's a phone call. You just need a compatible fax machine for it to work.