What Is a Thermal Fax Machine?
A facsimile or "fax" machine sends a document image over telephone lines to a distant receiver. The fax is received immediately as a full-size paper copy of the transmitted image. All fax machines contain scanners which store the image, modems that carry out transmission, and printers. Thermal printers were popular in faxes from the 1980s until the early 2000s, when in many offices they were replaced by inkjet and laser printers.
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Fax Machines
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The technology of fax machines has been developing since 1843, since Scottish inventor Alexander Bain received a patent for the first telegraph device that could transmit visual information. Modern fax images come in the form of bits of data, with a bit defined as a region of either white or black, and the bits composed into a large grid known as a bitmap. In the 1980s a universal standard for transmitting fax images at the rate of 9,600 bits per second was adopted. Modern faxes transmit at different rates of speed, up to 28,800 bits per second.
Thermal Printers
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On the earliest faxes of the modern era, a heat-sensitive thermal printer was installed on fax machines that required a roll of "thermal" paper in order to work properly. Thermal paper comes in 8.5-inch-wide (the more common) and 10.1-inch-wide sizes. The chemicals used to coat the paper are sensitive to heat.
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Direct Thermal Method
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The thermal printer uses heat to operate. After arriving over the transmission line, the bits of data are translated into dots. In "direct thermal" technology, a printer head translates the dots into heat and burns the appropriate dark areas directly onto the coated paper. A small blade built into the fax machine cuts the separate pages before they come out of the machine.
Thermal Transfer Method
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A newer method known as thermal transfer has gradually replaced the direct transfer method. In this method, plain paper can be used instead of thermal paper. Ink is stored in the machine and is transferred to the page by a transfer ribbon, which is set between the printhead and the paper. There are three basic varieties of transfer ribbon: wax, resin, and a wax/resin composite. The resin ribbons provide the highest quality but are also the most expensive.
Advantages of Thermal Faxes
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Thermal fax machines do not require ink cartridges, therefore they are cheaper to operate than faxes with inkjet or laserjet printers. They have fewer moving parts and a simpler mechanism, therefore may be less prone to breakdowns. Thermal paper provides clear resolution, although the image tends to soften and the paper turn brittle over time. Stored thermal-printed documents will also yellow with the action of heat and light on the sensitive paper.
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References
Resources
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