Snom D715 Series Manual page 8

Transfer a Call
Attended Transfer
You do wish to introduce the call to party "C" (e.g. another extension)
Step 1 – While the call is connected, press the HOLD button on the Context Display.
Step 2 – Press the programmable
key or the extension number of
party "C" followed by 
Step 3 – If Party C wishes to accept the call, press XFER. Calls will be joined.
If Party C does not accept the call, press X to terminate the call.
Return to Party "B" (currently on hold) by selecting the flashing line.
Transfer Button
Hold Button
Programmable
Keys