A fax machine scans paper documents and converts them into digital format.

The digital version is then converted into analogue format and sent over an ordinary telephone line to another fax machine.

The fax machine at the receiving end converts the analogue information back into digital format and reproduces an exact hard copy of the original document.

Faxes are particularly useful for transferring images such as plans, drawings or documents with signatures between remote locations when it is important that an identical copy of the original is received at the other end.