Panasonic KX-FL511C Operating Instructions Manual page 26

2. Preparation
– a fax calling tone (slow beep) is heard, or
– no sound is heard,
press *#9 (pre-selected fax activation
code) firmly.
3. Replace the handset.
L The fax machine will start reception.
Note:
L You can change the fax activation code in
feature #41 (page 48).
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