A fax-back system consists of a computer with a fax board, a voice board and two telephone lines. The requester dials in and is told to please enter the number of the document they need (using the telephone keypad), or a code for a catalog of available documents. The document(s), or catalog of documents, are immediately faxed to the fax number the requester enters.

Fax-back systems can save a huge amount of labor, and are convenient for the requester because they are available 24 hours a day from any telephone.

Some systems can import faxable documents from your Web site, but keep in mind that color pictures fax very poorly to standard fax machines (there is software to transmit color faxes from computer to computer).