elecom Handbook * 187 FAX SERVERS Caller enters their extension number or telephone number, followed by a pound sign (# on the touch-tone dial pad). "The number you entered was If this is correct, press 1. Otherwise, press 9. " Caller presses 1. "Your fax will be delivered shortly.' The Fax-on-Demand transmits the requested document to the fax machine at the telephone number entered. The docu- ment should have a cover sheet that identifies the fax recipient as the person with the telephone or extension number that the caller entered when he requested the fax. Since the calls delivering the fax documents are made after the calls that request the documents, the fax callbacks can be queued. This way, the available fax ports in the call back system can be fully used. In some systems, Fax-on- Demand takes incoming calls when it is busy even though all the ports for faxing out might be in use. This possibility for delay is a consideration in building the application. As with each Fax Back application, you must consider how many out- side lines are available to handle the incoming and outgoing calls. Otherwise, although ports in the system may be free, if all available outside lines are in use, no calls, incoming or outgoing; will be possible. When designing Call Back Fax applications, remember that now the owner of the Fax-on-Demand pays for the call, rather than the caller, as is the case with Same Call Fax. Another consideration that may be a drawback of Call Back Fax is, since the documents may queue before being sent, it is possible that a fax will be sent to an unattended fax machine. This may not be the best approach for faxing confidential docu- ments or for controlling whether or not the fax has reached the intended recipient. 188 - The Telecom Handbook CHAPTER 9 Methods of Document Selection There are two basic ways of requesting a document from a Fax-on-Demand application: Fax Back from Audio (Spoken) Menus Fax Library Using Document Number Audio Menus The easiest way to support small Fax Libraries is through