Canon MultiPASS C50 Software User's Manual page 154

Paper Size
You select the size of the paper you are using for printing a fax.
Reduce to Fit Paper
You specify whether you want an incoming fax reduced to ensure the
contents fits on the paper on which it is printed. If you want to reduce
the incoming fax, you can fit to height only, or both the height and
width, to fit the paper size.
Answer Receive Mode
You select the mode by which you want the C50 to receive incoming
calls:
Automatically switch for receiving a call either as a fax or
telephone call
Automatically receive only fax calls
Require you to manually answer the incoming call and then set
the C50 for an incoming fax
Chapter 8 C50 Setup and Other Utilities in the Desktop Manager 8-11