How do fax machines work?

What is a fax machine?

Short for facsimile which means ‘making an exact copy of’, the telecopying, telefax or fax machine allows a person to send a scanned image of a document or picture to another fax machine or the like.

When another machine receives the information, it interprets the document and reconstructs the image, printing it as a paper copy.

The machine is made up of a rotating drum and a small photo sensor with a lens and light. A paper document is attached to the drum with the print facing outwards, to start the faxing process.

The Process

• Scanning: The photo sensor focuses in on a very small spot on the piece of paper. This spot would either be black or white depending on whether there was print in that area. The drum would rotate allowing the photo sensor to examine one line of the piece of paper and move on to the next. A fax machine records the information of every dot in order to send the information to create a replica.
• Transmission: Before the sending process can take place, a signal needs to be recognised with another fax machine. Just like with a telephone, the other machine needs to acknowledge the ‘call’ before the transmission of information can begin. The sending machine will signal a connection with a series of beeps as will the receiving, which is a way of both machines checking for compatibility. Once this has been established the information can be sent.
• Confirmation: At the receiving end, a similar rotating-drum mechanism would operate alongside a pen feature which would leave marks on another piece of paper. For every white mark found on the existing document, the pen would not leave a mark; for every black mark found, the receiver would leave a dot. The 1,300-Hertz tone correlated to a dot and the 800-Hertz tone to a blank. The original document or image would be replicated completely and printed out.

Fax Machines in the 21^st Century

Modern fax machines work a lot quicker than original machines and have a slightly different design. Although they have been under pressure from a lot of modern technology as well as internet communication, they are still useful to many businesses and offices. Faxes are particularly advantageous for transmitting sensitive material which may be comprised or vulnerable to interception if sent over the internet.