FAX files supports two standard resolutions:
High quality 204x196 DPI
Standard quality 204x98 DPI
The High quality images look fine for displaying without resizing or zooming. This is the mode used when the "High quality mode" used on the fax machines.
The Standard quality images will look squished when displaying without resizing or zooming. In order to view the image properly, you should resize the image to expand the image's height twice.
This is the mode used when send faxes as "High quality mode", is not selected. When a fax machine receives such images, they double the height of the faxed image automatically.
Fax machines support the standard quality mode to reduce the time required to fax something to the half. When the image's height reduced to the half, the required transmission time will be reduced to the half, too.