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`How Fax Machines Work
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`BY MARSHALL BRAIN TECH | FAX MACHINES
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`Modern
`Fax
`Machines
`
`Panasonic KX-FB421 Fax/Copier machine
`PHOTO COURTESY PANASONIC AND MATSUSHITA
`ELECTRIC CORPORATION OF AMERICA
`
`A modern fax machine does not have
`the rotating drums and is a lot faster, but
`it uses the same basic mechanics to get
`the job done:
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`http://electronics.howstuffworks.com/gadgets/fax/fax-machine2.htm[12/8/2016 11:29:59 AM]
`
`Papst Licensing GmbH & Co. KG's Preliminary Response - Ex. 2005, p. 1
`
`
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`Modern Fax Machines - How Fax Machines Work | HowStuffWorks
`
`At the sending end, there is
`some sort of sensor to read
`the paper. Usually, a modern
`fax machine also has a
`paper-feed mechanism so
`that it is easy to send multi-
`page faxes.
`There is some standard
`way to encode the white and
`black spots that the fax
`machine sees on the paper
`so that they can travel
`through a phone line.
`At the receiving end, there
`is a mechanism that marks
`the paper with black dots.
`
`A typical fax machine that you find in an
`office is officially known as a CCITT
`(ITU-T) Group 3 Facsimile machine. The
`Group 3 designation tells you four things
`about the fax machine:
`
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`http://electronics.howstuffworks.com/gadgets/fax/fax-machine2.htm[12/8/2016 11:29:59 AM]
`
`Papst Licensing GmbH & Co. KG's Preliminary Response - Ex. 2005, p. 2
`
`
`
`Modern Fax Machines - How Fax Machines Work | HowStuffWorks
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`http://electronics.howstuffworks.com/gadgets/fax/fax-machine2.htm[12/8/2016 11:29:59 AM]
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`Papst Licensing GmbH & Co. KG's Preliminary Response - Ex. 2005, p. 3
`
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`Modern Fax Machines - How Fax Machines Work | HowStuffWorks
`
`The scanning process: The scanner in a fax machine
`looks at one line of the sheet of paper. The scan line
`is shown here in red. It sees a group of black and
`white spots, shown blown up in the red rectangle at
`the bottom of the figure. It encodes the pattern of
`spots and sends them through the phone line.
`It will be able to
`communicate with any other
`Group 3 machine.
`It has a horizontal
`resolution of 203 pixels per
`inch (8 pixels/mm).
`It has three different vertical
`resolutions: Standard: 98
`lines per inch (3.85 lines/mm)
`Fine: 196 lines per inch (7.7
`lines/mm) Super fine (not
`officially a Group 3 standard,
`but fairly common): 391 lines
`per inch (15.4 lines/mm)
`It can transmit at a
`maximum data rate of 14,400
`bits per second (bps), and will
`usually fall back to 12,000
`bps, 9,600 bps, 7,200 bps,
`4,800 bps or 2,400 bps if
`there is a lot of noise on the
`
`http://electronics.howstuffworks.com/gadgets/fax/fax-machine2.htm[12/8/2016 11:29:59 AM]
`
`Papst Licensing GmbH & Co. KG's Preliminary Response - Ex. 2005, p. 4
`
`
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`Modern Fax Machines - How Fax Machines Work | HowStuffWorks
`
`line.
`
`The fax machine typically has a CCD or
`photo-diode sensing array. It contains
`1,728 sensors (203 pixels per inch), so it
`can scan an entire line of the document
`at one time. The paper is lit by a small
`fluorescent tube so that the sensor has
`a clear view.
`
`The image sensor looks for black or
`white. Therefore, a single line of the
`document can be represented in 1,728
`bits. In standard mode, there are 1,145
`lines to the document. The total
`document size is:
`1,728 pixels per line * 1,145
`lines = approximately
`2,000,000 bits of information
`
`To reduce the number of bits that have
`to be transmitted, Group 3 fax machines
`use three different compression
`techniques:
`
`Modified Huffman (MH)
`Modified Read (MR)
`Modified Modified Read
`(MMR)
`
`See Electronics Plus: Facsimile Theory
`for a discussion of these compression
`types. The basic idea in these schemes
`is to look for "runs" of same-color bits.
`For example, if a line on the page is all
`white, the modem can transmit a dozen
`
`http://electronics.howstuffworks.com/gadgets/fax/fax-machine2.htm[12/8/2016 11:29:59 AM]
`
`Papst Licensing GmbH & Co. KG's Preliminary Response - Ex. 2005, p. 5
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`
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`Modern Fax Machines - How Fax Machines Work | HowStuffWorks
`
`or so bits rather than the full 1,728 bits
`scanned for the line. This sort of
`compression can cut transmission time
`by a factor of at least two, and for many
`documents much more. A document
`containing a significant amount of white
`space can transmit in just a few
`seconds.
`
`On the next page, we'll talk about
`receiving faxes.
`
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`
`Papst Licensing GmbH & Co. KG's Preliminary Response - Ex. 2005, p. 6
`
`
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`Modern Fax Machines - How Fax Machines Work | HowStuffWorks
`
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`http://electronics.howstuffworks.com/gadgets/fax/fax-machine2.htm[12/8/2016 11:29:59 AM]
`
`Papst Licensing GmbH & Co. KG's Preliminary Response - Ex. 2005, p. 7