Fax or facsimile is a device used for transmission of a written document, photograph, map or any other graphic material electronically. It is one of the variants of e-mail. For transmission the original document is placed in the facsimile or fax machine which scans the document and converts the written or graphic information into electronic signals and establishes a link-up with a similar receiving fax machine at the receiving end. The receiving fax reconverts the electronic signals into written or graphic form. As the sending machine scans the documents, the receiving machine reproduces the scanned image which is an exact duplicate of the originals. A typical fax machine can transmit a document of A-4 size in less than a minute over thousands of kilometres. Since fax operates through the normal telephone lines, the fax number is usually a telephone number. Also the same STD and ISD codes are used for sending a fax to another city or another country. The document is scanned page-by-page in the fax machine. Like the e-mail, fax communication eliminates the postal delay and is very convenient for communication between persons located in different time zones, but it costs more than the e-mail.