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阅读理解
Over the past 10 years, technologies that have combined computers with telephone have developed．Technologies such as PC fax programs and LAN fax servers(局域网传真服务器)have been used to improve fax communications．The latest computer-based technologies are new mechanisms(机制)which use IP(Internet Protocol, 因特网协议)to send faxes, that is, IP fax．
Traditional fax has a fairly simple usage model．First, the user inserts a document into the fax machine, enters the destination fax number and presses the starts button on the machine．The sending machine dials the receiving fax machine． If it connects, the sending machine scans the documents and sends it over the public switched telephone network(PSTN，公共电话交换网)to the receiving machine．At the same time, the receiving machine receives the document and then prints it．
In IP fax system there are two basic transmission modes：store-and-forward mode and real-time mode．Store-and-forward mode has been widely used．In this mode, the entire document is sent to a network-based server that stores it and then sends it to the destination．Real-time IP faxing is similar to traditional fax．Real-time mode allows two fax machines to directly communicate through some standard．
IP fax enabled a fax document to be sent from one person to another．A fax machine or a computer can be used to send or receive the fax．IP fax also allows e-mail to be used to receive faxes．This would enable users to receive faxes anywhere, anything with an internet fax address．
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