This description is taken from ECMA-269, Section 6.7.2,
"Monitoring".
6.7.2 Monitoring
To track call control and other activity, and to receive notification of
all changes in the switching Function, the
computing function uses a feature called monitoring. By starting a
monitor, the computing function indicates that it
wants to be notified of specific changes that occur in the objects
(call and device) and device attributes of a
switching function. Examples include:
-
Notification that a call has arrived at a device.
-
Notification that a call has been answered.
-
Notification that a feature such as �Forwarding� or �Do Not Disturb� has
changed at a device.
Once a monitor is established, the switching function notifies the computing
function of relevant activity by sending
messages called event reports, or simply events.
For example, in the area of Call Control, events report the state transitions
through which connections pass. In this
way a computing function is able to determine what services are applicable
to a given connection. For example, the
Delivered event indicates when a connection state transits to the Alerting
state.
The event categories are as follows:
-
Call Control - These events report changes to information related to calls.
-
Call Associated - These events report changes to information related to
calls.
-
Media Stream - These events report changes associated with attachment of
a call to a media device.
-
Physical Device - These events report changes to the components of a device's
physical element.
-
Logical Device - These events report changes to feature settings associated
with a device's logical element(s).
-
Voice Unit - These events report changes to Voice Unit messages.
-
Maintenance - These events report changes regarding maintenance.
-
Private - These events are switching function specific.