9513-023
Where to Connect the Telephone Line (MF275dw / MF274dn)
Connect the telephone line to the telephone line jack 
.
.MF275dw / MF274dn
When connecting an external telephone or an optional handset,
To the jack on the machine
When connecting an external telephone or optional handset: Connect to
(handset or external telephone jack) of the machine.
When connecting an external telephone or optional handset: Connect to
(handset or external telephone jack) of the machine.MF275dw / MF274dn
If you connect an external telephone with fax functionality, disable the automatic fax receive settings on the telephone.