Panasonic KX-FC966FX Operating Instructions Manual page 29

5. Fax
Note:
L Make sure feature #73 is set to "TEL/FAX"
beforehand (page 44).
How phone calls and faxes are received
If the call is a phone call, the fax machine will ring.
If a fax calling tone is detected, the fax machine will
receive the fax automatically without ringing.
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