There are two type of calls which your phone can automatically answer so that you hear the caller without taking any action. This will only happen if your phone is currently idle, ie. not on another call.
A call connected automatically after three beeps is a direct voice call to your extension only.
1.The call is connected and answered automatically. You can speak to the caller without taking any further action.
A call connected automatically after a single beep is a page call a group of which your phone is a member. You can hear the caller but they cannot hear you.
1.To answer the call, turning it into a normal call between just you and the caller, press the MIC/HFAI button.
While listening to page call, you can press an appearance button to make, answer or join another call. When you do this, the page call is disconnected and the new call is connected. However, the new call is connected as listen-only (microphone off and speaker on). In order to speak on the call, you needs to lift the handset or touch the Mic/HFAI button.