Here is the process of answering calls on Cisco 8851:
Answer a Call
When your phone rings, press the flashing line button to answer the call.
Answer Call Waiting
When you are on an active call, you know that a call is waiting when you hear a single beep and see the line button flash.
Press the line button.
(Optional) If you have more than one call waiting, select an incoming call.
Decline a Call
You can send a ringing call to your voicemail system or to a preset phone number.
Decline a call by performing one of the following actions:
Ignore a Call
If you do not want to be disturbed, you can ignore an incoming call. The call goes to voicemail.
Ignore a call by performing one of the following actions: