The StartEventSubscription function can be called by application software to subscribe to an event offered by another telephony device or application.

The StopEventSubscription function can be called by application software to terminate an event subscription. After application software calls this API procedure, the application will no longer receive events from the telephony device offering the event.

The TriggerSubscription function can be called by application software to trigger a re-subscribe to a previously subscribed telephony event. Normally the media engine will handle all of the details associated with event subscriptions and the renewal of those event subscriptions.