Brother MFC-3420C - Manual (Page 90)

4 - 14 USING THE WINDOWS ® XP-BASED BROTHER SMARTUI CONTROL CENTER
Fax
Send a Fax (Brother PC-FAX)—enables you to scan a page or
original and automatically send the image as a fax from the PC using
the Brother PC-FAX software.
Custom
Scan to File—These buttons have been pre-programmed for the
Scan to File feature. You can change the configuration of each of
these buttons to meet your specific requirements by right-clicking on
a button and following the configuration menus.