Call Waiting can only be performed on phones with a second line. If a call is placed to an extension, while already on another call, the speaker will provide a call waiting tone, and the phone will show a menu with the new caller's information. Two buttons are available to Answer and Reject the call. Should you answer the call, your existing call will be automatically placed on local hold, and you will be connected with the new caller. Once you have Parked or Transferred the call, you may then pick back up the original call by select the line key marked with the call. Reject will automatically send the caller to your voicemail, or other timeout destination.
There is no need to put the existing caller on hold or park, pressing Answer will automatically put the call on local hold.