Tatiana Alves da Silva,
Jaguariuna, SP
We thought that the fax was already a little out of fashion, but it seems that we were wrong! Let’s kill the curiosity: to transmit images and texts, the fax brings within itself three other technological gadgets that we know well:
1. The scanner, which “reads” the image to be transmitted and converts it into a digital file;
2. The modem, which converts digital data into electrical signals;
3. The telephone line, which transmits the electrical signals to the other fax machine.
Well summarized, this is the current process. When the device was created, things were different. The fax – or at least its basic principle – was patented in 1843 by the Scottish mechanic Alexander Bain. Combining the technology of telegraph transmissions with a clockwork mechanism, he invented a contraption capable of receiving signals from a telegraph line and «translating» them into drawings on a sheet of paper. Before falling into popular taste, the device had to wait almost 150 years: only in the 1980s, telecommunications companies developed a technology to make image transmissions faster. With the arrival of the Internet, the use of fax decreased, but it did not completely disappear because of its low cost and simplicity. After all, there are still a lot of people who know how to use a fax, but not an email…
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2. Scan information is stored in a memory. The data indicate, in computer language, the parts crossed by the light and the stretches where the light was interrupted. At the end of this phase, the image has become a digital file, a huge number full of zeros and ones — the white dots are assigned a value of 0 and the black ones, 1
3. The digital file goes to the modem, where it is transformed into an electrical signal. Numbers 0’s give rise to signals with a frequency of 800 hertz, while numbers 1’s become signals with a frequency of 1300 hertz. In the form of electricity, the document is released on the telephone line
4. On the other side, the receiving fax machine performs the reverse process: first, it transforms the electrical signals into digital data. It then transmits the digital data to a printer, which decodes the message and prints a black-and-white copy of the document. And ready!
It is the traditional fax paper, very thin and sold in reels. It is still used because it is economical as it does not need toner or ink. The secret is that the paper already comes with the “ink”: in thermal printing, a beam of light heats the printed regions, which turn black with the heat. It is because of the heat of the hands that sometimes we get our fingers dirty when picking up a fax.
SULFITE SHEET
More modern devices work with inkjet printing. The process is just like that of a computer printer: the device receives information and transmits it to the print head. Then she shoots thousands of drops of ink in the places that should be black, dotting the drawing