Sharp FO-880 Operation Manual page 20

Connections
Extension phone (optional)
If desired, you can connect an extension phone to the TEL. SET
socket on the fax.
1
Remove the seal covering the TEL.
SET socket.
2
Connect the extension phone line to
the TEL. SET socket.
Important: In New Zealand, not all standard telephones and
answering machines will respond to incoming ringing when connected
to the extension socket of the equipment.
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