Canon PIXM MX300 Series User Manual page 90

Note
If you do not have a dedicated phone line for fax use only, you need to
connect a telephone or an answering machine to the External device jack
of this machine.
If You Want to Receive Only Faxes Automatically with the Machine, or
Have a Dedicated Telephone Line for Fax Use Only:
Select FAX ONLY MODE.
Incoming call
(A)
Receives faxes automatically.
(B)
Note
You will not be able to answer the call.
If You Are Using a Single Telephone Line for Faxes and Voice Calls and
Use Voice Calls More Frequently:
Select TEL PRIORITY MODE.
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