How many kinds of fax machines are there?

Lead: How many types of fax machines are there? Fax machines can reproduce the original works intuitively and accurately, and can transmit charts and photos that are difficult to express in words. It is simple to operate and widely used in military communication. Therefore, with the development of science and technology, there are many kinds of fax machines and their classification methods are also different. According to their uses, they can generally be divided into the following categories. Let's get to know each other.

There are several types of fax machines: photo fax machines.

It is a fax machine, which is used to transmit continuous tone images in all optical density ranges, including black and white, and copy copies that meet the requirements of specific tone density through photographic records. Photo fax machines are mainly used in news, military and medical departments. The photo fax machine transmits images in continuous tones (including all optical density ranges of black and white), and the receiver uses photographic paper (or negative) for photosensitive recording. In order to make the replica reach a certain tone density level, tone correction measures are taken in the receiver. There are two types of photo fax transmitters: fixed desktop and portable, which adopt roller scanning; The receivers are mostly fixed desktops, which adopt roller scanning or plane scanning. In the telephone circuit, you can choose amplitude modulation or frequency modulation according to the transmission needs. Photo fax machines are mainly used in news, public security, military, medical and other departments.

Two: newspaper fax machine

It is a fax machine, which scans and sends a full-page newspaper proof, and the receiver copies the film through photographic records for plate making and printing. In order to ensure the timeliness and accuracy of newspaper news, there are high requirements for the copy quality and transmission rate of newspaper fax machines. Analog newspaper fax machine mainly uses cable or microwave carrier telephone system to transmit on broadband base group or super group channel, and can also be equipped with data compression equipment to transmit on analog or digital channels. Digital newspaper fax machine mainly adopts digital channel transmission of satellite communication system. There is also a newspaper fax machine, called the user newspaper fax machine, which is installed at home or office and is usually used to receive fax programs (full-page newspaper information or weather forecast, etc.). ) broadcast by radio or TV stations, and directly recorded on paper for display.

Three: Meteorological fax machine

It is a fax machine for transmitting meteorological cloud pictures and other meteorological pictures, also known as weather map fax machine, which is used in meteorological, military, aviation, navigation and other departments to transmit and copy meteorological pictures and cloud pictures. The transmission format is larger than newspaper, but the resolution requirement is not as high as newspaper fax machine. It mainly uses wireless broadcasting to send and receive signals. The receiver is remotely controlled by the transmitter, which can automatically start and stop, select scanning parameters and adjust the receiving level. In addition, there is a satellite cloud picture fax machine, which receives cloud pictures and infrared pictures taken by meteorological satellites, and requires high resolution and tone. There are two transmission modes of meteorological fax, namely short-wave (3 ~ 30 MHz) meteorological wireless fax broadcasting and point-to-point meteorological transmission broadcasting using wired or wireless circuits. Meteorological fax broadcasting is a one-way transmission mode, and most meteorological fax machines are only used for receiving.

Four: color fax machine

For news or military departments to transmit and copy color photos or color maps.

There are basically two ways to send color pictures by fax:

One is adoption? Sequential transmission? That is to say, the color image information is decomposed into three basic information: red, green and blue, and then transmitted in turn, and then the three primary colors are mixed at the receiving end to reproduce the same color image as the transmitting end. Using this method to transmit, it takes three times as long as sending black-and-white images, and four times as long as containing black.

The second is adoption? Simultaneous transmission? That is, separate signals of each color are transmitted at the same time, but this requires increasing the bandwidth of the circuit.

Five: document fax machine

This is a fax machine, which copies the original with black and white optical density grade. It is mainly suitable for copying handwritten, typed or printed documents, charts and halftone images with limited black and white levels. Widely used in office, transaction processing and other fields. According to the difference of using telecommunication network, signal processing technology and standard format manuscript transmission time, document fax machines can be divided into one type for public telephone network, two types for public data network, three types for fax machines and four types for fax machines.