A call is a communication session between two endpoints: a local endpoint and a remote endpoint. Microsoft Unified Communications Managed API (UCMA) 3.0 represents the call concept by the Call abstract class, and provides non-abstract classes that implement three specific types of calls.
An InstantMessagingCall instance is used in a communication session for which the media type is Message, or text.
An AudioVideoCall instance is used in a communication session for which the media type is Audio.
The default media provider for the AudioVideoCall class does not support the Video media type.
A BackToBackCall instance represents a logical SIP network element that mediates SIP signaling between two call legs. A BackToBackCall instance can be used to connect two clients that send and receive audio alone or audio and video.
This section describes common operations that a UCMA-based application performs on calls.