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Phone Fax Machines - How Do Phone Fax Machines Work?

document line sent white

The following information will discuss how phone fax machines work. The goal designed into the phone fax machine was to replicate the original document at the sending end. Send that document via phone line to the receiving phone fax machine at the other end. This is why it is called a phone fax machine. It is a fax machine with a phone line and a phone handset. You can talk to another person as it is a phone connected to a phone line or dial another phone fax and send a document to that receiving phone fax. The phone fax will copy and send a black and while facsimile of the original document via phone line.

Fax machines are used in many ways. They are the only way to send an important document quickly and reliably. Email has been trying to replace phone faxing but using a fax machines is the only way to provide an exact copy of an original without possibility of tampering. Owning a reliable fax machine is still an essential part of any business and now many households have them also.

Early phone fax machines used a simple technique of white and black symbols. A tone for white was sent if the spot read by the fax sensor was white and a black spot sent out a different signal. A rotating arm over a drum would read the document and send the signals then the rotating arm on the receiving end would translate the signals and either put a black dot on the paper or leave a white space.

Modern phone fax machines don’t have rotating drums and the document is sent much faster and more accurately. The white and black dots on the document are still scanned by a sensor which compresses the block of data and encodes it for transmission. The sensor scans the document on line at a time. A line to the sensor is 1,722 bits in standard mode. Lines per page are 1,145 bits. The sensor reads the line by the help of a small florescent tube that lights the document from the back giving the sensor a clear and precise picture. The sensor reads the group of white and black spots and encodes the spot pattern. The encoded information is sent via phone line to the receiving machine. The receiving machine translates the encoded signal marking the paper with the same patterns of white and black dots that were sent.

Modern faxes have the capability to change the resolution on the document. Two vertical resolutions are common.
• Standard – 98 lines/inch
• Fine – 196 lines/inch
A third resolution is possible on some machines – 391 lines/inch

Data is transmitted over the phone line at a rate of 14,400 bits per second (bps). Some phone fax machines are a little slower using 12,000 bps down to 2,400 bps. Older machines use the lower end as at the time it was the highest rate possible.

When the receiving phone fax machine gets the encoded message, it decodes the bits sent over the phone line, takes the compressed signal and pulls the bits together writing the black dots on the paper and leaving the white areas alone.

Different phone fax machines receive and print the documents differently.

Laser printer – most popular Inkjet – cheaper than laser but quality not quite as precise Computer printer – prints file sent via fax modem to computer then sends file to the printer Thermal paper – earliest phone fax machines used this Thermal film – ink melted onto paper through heating

Multiple page documents can now be sent more easily and faster than with the original phone fax machines. The scanner scans all the pages into memory. The fax will connect with a digital handshake between the two machines. After the connection is established, the document pages are sent. The sending fax machine will print a confirmation sheet indicating if the fax was successful or not. The receiving machine will store the document in memory, print the faxed document and both machines will terminate the connection.

Phone fax machines are a necessary tool used to transmit documents over long distances in a minimum of time. Email and snail mail are also used for this purpose. Email cannot replace everything a fax represents. Snail mail takes precious time that may not be available. Faxes are considered by some processes the same as the original copy which keeps phone fax machines at the height of business tools needed. They have become common to most households in order to provide quick document transfer and quick receipt over long distances saving time and money for the user.

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