Sharp UX-305 - Manual (Page 66)

How the hookup operates
While you are out, all of your incoming calls will be answered by your
answering machine and its outgoing message will play. Voice callers
can leave a message. During this time, your fax will quietly monitor
the line. If your fax detects a fax tone or a duration of silence greater
than four seconds, it will take over the line and begin reception.
When you return and
turn off your answering
machine, be sure to
change the reception
mode back to FAX or
TEL!
Activating the Answering Machine Hookup
64