Fax Machines

Please note that this chapter is in outline form and will be fleshed out later. Use it to guide you through your own research.

Passes paper over narrow slit in a black mask

Shines light on paper exposed through slit

Focuses image on row of photo receptors

Scans photo receptors to find white and black parts of paper.

Sends a tone over telephone, one frequency for white another for black.

Receiver uses tones to switch a row of tiny heaters on and off.

Heaters cause heat sensitive paper to turn black when tone indicates black on paper.

Paper advance by heaters as signal is received to rebuild original image.

Modern digital fax machines use multiple tones to send more data at one time - Also use data compression to increase data rate

Technology easily adapted to scanners and printers.

Answering fax machine sends tone to indicate that it is a fax machine

The two machines send multiple tones back and forth to determine the speeds and protocols available to communicate (the handshake)