Appearance buttons are used to represent calls made and received by you and other users on the telephone system. They are configured by your system administrator. Normally, your first three buttons are call appearance buttons, but your administrator can configure additional appearance buttons for you if required.
There are several different types of appearance button:
•Call Appearance Buttons
These buttons are used to make and answer general calls.
•Bridged Appearance Buttons
This type of button mirrors another users call appearance buttons and allows you to make and answer calls for a colleague.
•Call Coverage Buttons
Be alerted when a colleague has unanswered calls and answer those calls.
•Line Appearance Buttons
Make and answer external calls on a particular telephone line.
Those buttons not programmed as appearance buttons can be programmed as feature buttons.
Which appearance button is currently selected and gets used when you go off-hook, for example by lifting the handset, is controlled by two system settings which are normally on by default. Those settings are:
Idle Line Preference
Idle line preference automatically selects the first available call appearance or line appearance button as your currently selected button when you do not have a call connected. This means it will be the appearance button used when you go off hook. If this was not the case, you would need to select an appearance button before going off hook to make a call.
Ringing Line Preference
If not connected to a call, when you receive an incoming call, ringing line preference automatically makes the alerting appearance button your selected appearance button. This means that you can answer the call by simply lifting the handset or pressing the Headset 
or Speaker 
button.
Without ringing line preference, to answer the call on the alerting appearance button you must first press that appearance button to select it.