Communication Path 

ACCESSAPHONE TO PHONE

When using accessaphone, the application will communicate with windows TAPI. TAPI will communicate with the Phone System TSP and the Phone System TSP will communicate with the VoIP/PBX Switch. Finally, the VoIP/PBX Switch will communicate with the phone.

PHONE TO ACCESSAPHONE

When the phone rings, the VoIP/PBX Switch notifies the Phone System TSP of the event then the TSP notifies TAPI which then notifies accessaphone.

See the diagram below for a visual regarding the above mentioned communication path.