Faxes transform printed matter into a complex series of dots, similar to a bit-mapped graphic image.
A fax can be sent using hardware very similar to a modem which translates these dot patterns into analogue signals and transmits them over phone lines to another fax that decodes the signals and prints out the image. This can also be achieved using digital communications methods. A typical fax terminal looks like a small desktop photocopier. It scans and prints pictures using the same principles. A basic fax machine can transmit and receive A4 size documents, and many machines have added services such as automatic dialling and the transmission of documents of various standard sizes.