This is why your fax should always be accompanied by a cover note. This note should not be your standard cover letter. Because for starters, you should still send them your cover letter by mail, along with your regular resume. A fax is never a substitute for the real thing. A faxed resume is a temporary document only to be used until a good copy on high quality paper can arrive by mail.
Faxes are for the high-speed transmission of data.
A note is fast, to the point, and provides the reader with less faxed copy to try and read. I am very enthusiastic about this position. Your note should also let them know exactly how many pages you are faxing and where you heard about the job. A professional looking presentation is usually taken more seriously than something that looks like it was sent out on the spur of the moment. If there is no deadline and time is not of the essence, rely on the mail and not a fax.