Co-existence is when an incoming call is forked between the PBX phone and the user who is logged on to Office Communicator 2007 R2 endpoints; both the PBX phone and Office Communicator 2007 R2 co-exist for a user. The result is a mix of PBX and Office Communications Server 2007 R2 communication capabilities configured for call routing using IP-PBX integration between the user's legacy phone and Office Communicator 2007 R2.

Remote call control (RCC) allows Office Communicator 2007 R2 to control a user's PBX phone line and indicate their presence based on the status of their phone. Users can answer their PBX phone with Office Communicator 2007 R2 and update their presence to "In a Call."

This figure demonstrates TelephonyMode=2 for a call placed from a PBX phone and received using either the recipient’s PBX phone, or from the recipient’s Communicator 2007 R2 client.

As shown in this figure, the following activities occur:

Step 1:PBX Phone User B places a direct call to PBX Phone User A. The PBX phone for User A rings. The PBX phone can be answered.

Step 2:While the PBX phone for User A is ringing, User A receives a notification from Communicator 2007 R2 to receive the call by using Communicator. The Communicator client can be used to answer the call by using RCC.