Panasonic KX-TDA15 User Manual page 69

SLT
During a conversation
OR
C.Tone
Press Recall/
hookswitch.
extension no.
Dial the other party's
extension number.
1.4.3 Talking to Two Parties Alternately (Call Splitting)
OR
Talk to the
Press Recall/
hookswitch.
other party.
On-hook.
User Manual 69