Panasonic KX-TG2631 Operating Instructions Manual page 22

Making/Answering Calls
emphasize existing line noise. If it
becomes difficult to hear, turn this
feature off.
Call share
Available model:
KX-TG2632
This feature allows the handset to join an
existing outside call.
To join the conversation, press {C} when
the other handset is on an outside call.
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