The fax machine decomposes the original to be sent into many tiny units (called pixels) by the optical scanning system in a specified order, and then the brightness information of these tiny units is converted into electrical signals by photoelectric conversion devices in turn, which are amplified, encoded or modulated and sent to the channel. After amplifying, decoding or demodulating the received signal, the receiver copies the original in the form of recording at the same scanning speed and order as the transmitter.

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.

The inkjet/laser all-in-one machine should first point out the diversity of functions. In addition to ordinary fax and copy functions, the all-in-one machine can also be connected to a computer for printing and scanning operations, and some can also save faxes to the computer, thus saving paper and ink. By installing related software, the functions of sending fax and printing to fax can be realized. In the menu design, various parameters of the manuscript to be faxed can be conveniently set on the panel of the inkjet/laser integrated machine, and functions such as color copying and color fax can also be realized. In the automatic pagination function, the inkjet/laser integrated machine can automatically feed paper page by page, making fax transmission convenient and fast.