What is the principle of fax machine?

Although the fax machine is a communication tool that has been widely used in recent 20 years, its invention idea was formed 50 years ago. According to relevant data, as early as May 27th, 1843, the principle of fax machine was patented, which was 30 years earlier than the telephone patent.

The working principle of fax machine is actually relatively simple. Firstly, the documents to be faxed are converted into digital signals in huffman encoding mode by photoelectric scanning technology, then converted into audio signals by V.27 and V.29 modulation, and then transmitted through traditional telephone lines. After receiving the signal, the receiver's fax machine will recover the signal and print it out, so that the receiver will receive a copy of the original document. To sum up, when sending: scan the picture-> Generate data signal->; Digital information compression->; -> modulated into analog signals; When sending to the telephone network for sending and receiving: receiving analog signals from the telephone network->; Demodulate into digital signal->; Decompress the digital signal into an initial image signal->; Print.

Different types of fax machines have different printing methods after receiving signals, and their working principles in these aspects are basically different. There are two main types of fax machines on the market now: thermal paper fax machines and inkjet/laser fax machines.

The thermal paper fax machine melts and discolors the thermal materials on the printing medium through the thermal print head to generate the required characters and graphics. Thermal transfer printing is developed from thermal technology. By adding a thermal transfer ribbon, the ink coated on the ribbon is transferred to paper to form an image. Thermal printing is used in the most common fax machines.

Laser plain paper fax machine is a kind of fax machine that uses toner to attach to paper and images. Its working principle is mainly to use a selenium drum in the body to control the laser beam. By controlling the turn-on and turn-off of the laser beam, a charged image area is generated in the selenium drum. At this time, the toner in the fax machine will be attracted by the charge and attached to the paper to form words or images. The working principle of inkjet fax machine is similar to dot matrix printing. The inkjet head is driven by a stepping motor to move left and right, and the ink sprayed by the inkjet head is sprayed on ordinary paper in turn to complete the printing work.