Facsimile Transmission

I

Introduction

Facsimile Transmission, communication system that copies, sends, and receives documents by way of telephone lines. Also called faxing, this method of communication allows people to share exact copies of important papers by duplicating and sending them on one end, and then receiving and reproducing them on the other.

Facsimile machines came into use in the early 20th century when newspaper companies began using them to transmit photographs between branch offices. By the mid-1980s use of desktop facsimile machines had become commonplace for business and personal correspondence throughout the world. More recently, people have used personal computers to send and receive facsimile transmissions, or faxes, eliminating the need for a separate facsimile machine.

II

How Facsimile Machines Work

The standard facsimile machine works like a combination telephone and photocopier. The user places the documents into a document feeder on the sending machine, then dials the telephone number of the receiving fax machine. A gear mechanism pulls the original document over an optical scanner. The scanner records variation between light and dark areas of the document as dots arranged in a series of rows or columns. A photoelectric cell converts the dots into electronic impulses, which are then transmitted to the receiving fax machine via telephone lines.

The receiving fax machine decodes the electrical impulses into a series of dots. It sends the decoded signal to a print mechanism built into the fax machine, which prints a duplicate of the original document. International standards ensure that fax machines around the world are compatible with each other.

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Older fax machines use special thermal (heat-sensitive) paper, which passes over wires that are heated in response to the electrical impulses transmitted by the sending fax machine. The thermal paper darkens when exposed to the heat of the wire to create a copy. Newer fax machines use small laser printers or ink-jet printers built into the fax machine to reproduce documents.

III

Computer-Based Faxing

Personal computers can mimic the operation of fax machines. Computer-based faxing enables people to transmit electronic computer files as faxes to another computer or to a conventional fax machine.

To send and receive facsimile transmissions, a computer must be equipped with faxing software and a fax modem, and it must be connected to a telephone line. The faxing software prompts the computer user to enter the fax number of the receiving computer or fax machine. The software compresses the file so it can be transmitted more efficiently, then sends it to the fax modem. The modem converts digital computer files into analog signals so they can travel via telephone lines.

The fax modem of the receiving computer reconverts the analog telephone signal into a digital computer file. The faxing software on the receiving machine decompresses the file, then notifies the computer user that a fax has been received. The receiver may choose to either view the fax in its electronic format or print it.

IV

History

Scottish physicist Alexander Bain patented the first facsimile device in 1843. The device generated electrical impulses by passing a metal rod over a page that contained raised metal letters. The electrical signal traveled along a wire to a receiving machine, which printed the signal on electrochemical recording paper. Bain’s system relied on pendulums to synchronize the sending and receiving machines.

German physicist Arthur Korn transmitted photographs from one device to another over telephone lines in 1902, but the basis for modern fax machines did not appear until 1925. In that year French inventor Edouard Beeline introduced the Belinograph. Beeline’s facsimile machine used a powerful light beam and a photoelectric cell to convert the light, or the absence of light, on an image into electrical impulses. Newspapers soon adopted this technology to send photographs from one office to another. Shortly thereafter, the Associated Press and the American Telephone and Telegraph Company established wire services for the routine distribution of photos to newspapers across the country.

In 1966 the Xerox Corporation began manufacturing a small facsimile machine that could be connected to any telephone line. In the years that followed, many other companies produced fax machines, each smaller, less expensive, and easier to use than its predecessors. By the end of the 1980s fax machines had come into popular use throughout the world.

In the 1990s many people turned to computers to send and receive faxes. In the latter half of the decade, Internet fax services grew increasingly popular. These services provide the ability to receive faxes to anyone who has Internet access.