HOW TO DO CALL TRANSFERS on GXP16xx:
You are in a call and wish to transfer the call to another extension number.
BLIND TRANSFER:
1.) Press the transfer button 
.
2.) Dial the Number and press the send button to 
complete transfer of active call.
ATTENDED TRANSFER:
1.) Press an idle line key to make a new call and the active line will be placed on hold automatically.
2.) Dial the extension/ number you want to transfer the call to.
3.) Once the call is established keep in the line for 10 Seconds.
4.) Press the transfer button 
5.) Press the Line button of the hold line to transfer the call and after the call is transferred, phone will display idle screen.