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Like just about every piece of modern technology today, its hard to imagine how we ever managed without the fax machine. It can take a page of information, scan it and send it speeding to the other side of the world.
Before fax, we used to rely on telex machines which allowed an operator to type in a text message, transmit it as a signal across the phone network and then use it to operate a remote teletype machine to output the text at the receiving end. This was adequate for western businesses whose languages used an easily encodable text form - the alphabet. The Japanese, who dont use an alphabet, but a graphical representation of words ie, a pictureform, had a real problem. They couldnt use a telex machine to send text information and so had to come up with a method for sending information in graphical form. Their ingenious solution to the problem was the fax machine. It optically scans a page of information, turns the graphical information into a stream of 1`s and zeroes, translates the digital data into an audio signal which it transmits over the phone line.
The receiving fax converts the audio data back into a digital form, reassembles the data in memory and then sends it to the print system which outputs a hard copy to the receive tray.

Original Feed.
When you place your original in the fax, program the receive number and press the start key, a rubber feed roller drives the sheet across a slim glass plate. The roller is driven by a stepper motor which, as its name suggests moves the sheet in small incremental steps. At each step a small section of the original is placed on the glass, illuminated by a small strip light, scanned and the next section of the image is brought forward in turn until the entire sheet has passed over the glass.

Scanning and Image Processing
At each step, a thin strip of the image falls onto an angled mirror below the glass plate. The mirror reflects the image into a lens which focuses it onto a special optical chip called a CCD
(charge coupled device). The CCD converts the white areas of the image into 1`s and the dark areas into zeroes and stores them in a temporary memory buffer. The CCD feeds the data out in a pulse which is synchronized with the incremental rollers. The data goes into the signal processing PCB which removes noise and compresses the data using special mathematical formulae called algorithms. The reason for data compression is to speed up the transmission speed on the phone network. The more image data on the page ,the longer it takes to transmit. You may have noticed that a page of text goes through the machine a lot faster than say a brochure with photographs.

Modem Encoding and Transmission.
Fax machines “talk” to each other by emitting a wave of a certain frequency onto the
telephone line. This wave is called the carrier. Generally, public telephone networks can only communicate using frequencies that are within the voice band, that is, between 300 and 3,400 Hz. Therefore, the carrier wave must be somewhere within these limits. The data signal from the fax machine is known as the modulating signal.
To transmit data using this carrier wave, the fax machine superimposes the modulating signal onto the carrier wave by varying the frequency, amplitude, or phase (or a combination of all three) in a standard manner. This process is known as modulation. The machine receiving this modulated signal can recover the original data by demodulating the signal. A device called a modem carries out modulation and demodulation. In fact, it takes its name from combining the first three letters of each word.

Reception and Printout
People often find it hard to relate to each other and exchange information without some kind of
formal introduction. Fax machines have similar problems.
Standard signalling procedures for fax machines have been developed so that any pair of fax
machines can communicate with each other, regardless of their makers or countries of origin.
Facsimile machine protocol allows handshaking between the two machines before and after data
transmission. Handshaking allows the machines to exchange identification and information on
what features they are equipped with. Also, the protocol allows the machines to determine the
optimum transmission speed for the communication.
So,the fax machine at the remote location goes online when it receives the incoming call. The two machines then go through their digital introductions to each other in which they sort out the speed of transmission and reception, paper sizes, optional features and telephone line quality. When the machines are synchronized data transfer begins.
The remote fax takes the modulated data from the phone connection and puts it through the modem which converts the tonal information back into digital form. The CPU reconstructs the page in memory and then outputs it to the printing section in order to provide a hard copy .