There are several options for sending and receiving faxes, including the following:
Traditional fax machines and computer-based faxing Scanners, a fax modem in a computer, a printer with built-in faxing capabilities, or a dedicated fax machine can be used to send and receive faxes. They are used to transmit data in the form of pulses by using a telephone line to another fax device, usually another fax machine or computer that has a fax modem. The pulses are then transformed into images or used to print the image on paper.
The traditional fax method requires at least a single telephone line on the sending and receiving device, and only one fax can be sent or received at a time. A disadvantage of sending and receiving faxes by using a fax modem is that the computer must be turned on and running fax software or a fax service. This kind of computer-based faxing does not use the Internet to send or receive faxes. The following figure illustrates how traditional and computer-based faxing is used to send and receive faxes.
Traditional and computer-based faxing.gif)
Fax servers or gateways and Internet fax services There are several ways to send and receive faxes over the Internet. These include using a software application on a computer or using an e-mail client to receive faxes. In most cases, this kind of faxing involves using a fax server or fax gateway to convert between faxes and e-mail. This has become increasingly popular because it enables organizations to remove or not purchase additional fax machines. It also eliminates the need to install additional telephone lines. This kind of faxing involves creating the document, including a fax cover page with the correct identifying information, and sending the document to a traditional fax machine. For example, the user uses a software application such as Microsoft Office Word or Microsoft Office Outlook to create and send the fax to the fax server or gateway. The fax server or gateway receives the fax and then sends it by using a traditional telephone line to a fax machine or fax modem that is installed on a computer. The following figure illustrates how fax servers, gateways, and Internet fax services can be used to send and receive faxes.
Faxing by using fax servers or gateways.gif)
Internet fax services let a user send faxes from a computer by using the Internet. A software application such as Office Word or Outlook can be used to create and send the fax to an Internet fax service. There are many companies that offer Internet faxing services on a subscription basis or by charging for each fax message that is sent. Internet fax services offer the following advantages:
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No fax machine is required
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No software or hardware must be installed
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No dedicated telephone lines are required
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Confidentiality
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Multiple faxes can be sent at the same time
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Faxes can be received when the computer is shut off
The following figure illustrates how Internet fax services can be used to send and receive faxes.
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Faxing by using an e-mail client application Faxes can be sent and received by a fax machine over the Internet and then received by an e-mail client such as Outlook.
The T.37 protocol was designed to enable a fax machine to send fax messages over the Internet to an e-mail client. The faxes are sent over the Internet as an e-mail attachment, typically as .tif or .pdf files. In this kind of faxing, a fax machine that supports iFax or T.37 is required, in addition to an e-mail address for the sending and receiving fax machines. To work with existing traditional fax machines and fax modems, all T.37 fax machines support standard faxing by using a telephone line. However, in some cases, T.37 fax machines can be used when a fax gateway is also being used. The following figure illustrates how T.37-based fax machines and e-mail clients can be used to send and receive faxes.
Faxing with e-mail.gif)
Faxing by using a VoIP network VoIP is a technology that contains hardware and software that enables people to use an IP-based network as the transmission medium for telephone calls. On a VoIP network, voice and fax data is sent in packets by using IP instead of by traditional circuit transmissions or the circuit-switched telephone lines of the PSTN. An IP gateway that you connect to your IP network uses VoIP to send voice data packets between an Exchange 2007 Unified Messaging server and a Private Branch eXchange (PBX) system. Alternatively, you can use an IP PBX to perform the functions of both an IP gateway and a PBX.
There are two basic types of networks: circuit-switched and packet-switched. A circuit-switched network is a network in which there exists a dedicated connection. A dedicated connection is a circuit or channel that is set up between two nodes so that they can communicate. After a call is established between two nodes, the connection may be used only by these two nodes. When the call is ended by one of the nodes, the connection is canceled. In circuit-switched networks, such as the PSTN, multiple calls are transmitted across the same transmission medium. Frequently, the medium that is used in the PSTN is copper. However, fiber optic cable might also be used.
In packet-switched networks such as the Internet or a local area network (LAN), packets are routed to their destination through the most expedient route, but not all packets traveling between two hosts travel the same route, even those from a single message. This almost guarantees that the packets will arrive at different times and out of order. In a packet-switched network, packets (messages or fragments of messages) are individually routed between nodes over data links that may be shared by other nodes. With packet switching, unlike circuit switching, multiple connections to nodes on the network share the available bandwidth. Packet-switched networking has made it possible for the Internet to exist and, at the same time, has made data networks—especially LAN-based IP and VoIP networks—more available and widespread. The following figure illustrates how a VoIP network and Exchange Unified Messaging can be used to deliver faxes.
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