The facsimile or fax machine was first invented back in 1842 by a
Scottish electrical engineer named Alexander Bain. This was about
five years after Morse invented the telegraph.A fax machine electrically
breaks up a document into very small pieces, which are called picture
elements or pixels and sends them one by one to another fax by way of
a phone line. The density of each element is converted to an electrical
current which is sent to the receiver. The receiving fax puts the
picture elements together as it receives them, until a copy of the
original is made.Facsimile (fax) technology, the transmission of images
over a telephone line, made its appearance in a commercial application
about 70 years ago in the form known as wirephoto, which was used to
transmit photographs for publication in newspapers. In the early
1960s, the development of modem technology made facsimile machines
practical, although the slow transmission time impeded widespread use.
However, in the early 1970s, image data compression was introduced,
which drastically reduced transmission time and enabled the fax
machine to become an integral part of the business environment.
Types Of Facsimiles:
- GROUP I ( G1 ) / Old FM Transmission time : Approx. 6 minutes per page
- GROUP II ( G2 ) Transmission time : Approx. 3 minutes per page
- GROUP III ( G3 ) Transmission time : Less then 1 minute per page
- GROUP IV ( G4 ) Transmission time : Approx. 10 seconds per page
The operation of a fax machine is strictly specified by the International Telegraph and Telephone Consultative Committee called "CCITT". This committee sets the standards for all fax equipment thereby allowing different manufactures and faxes in different countries to communicate with each other. Because fax machines are so easy to use (put the paper in the hopper, dial the number, and push the send button), many people assume that the whole process is very simple. The truth of the matter is that communications compatibility between fax devices is complicated and not problem free. Sending a fax is far more complex than just dialing a phone number and sending an image. The calling unit must first confirm that the call is being answered by an actual fax device rather than a data modem, answering machine, or human being. Once it is determined that two fax devices are talking to each other, these devices must then exchange information to find out what capabilities they both support (e.g., data transmission rate, image resolution, data compression schemes, paper size). They then must agree on a mutually supported subset of these capabilities. Next, the phone connection must be evaluated to determine the maximum practical data rate available. Finally, the fax image is sent. However, it is possible that noise or distortion will corrupt the image during its transit of the connecting network. To check for this possibility, the receiving fax device must evaluate the image and send an acknowledge message indicating whether the image was received correctly or whether it had an unacceptable number of errors. The protocol for sending or receiving a fax image and exchanging associated messages is defined in the International Telecommunications Union (ITU) Recommendation T.30. Fax technology continues to evolve, with new features being added on a regular basis, and new fax devices must be compatible not only with the latest models but also with the existing installed base of fax machines. Communications technologies and network structures are changing at a rapid pace (the Internet and cellular phone networks in particular), and all of these must be able to handle fax traffic as well as voice.
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