A group of users can be created with a purpose of receiving voice announcements through the speaker of a telephone set, but it has to be in the waiting mode.
A Media Gateway Control Protocol (MGCP) is a Voice over Internet Protocol system used to handle the exchange of information and the management of a multimedia conference session. The exchange of information, known as signaling, is responsible for connecting, controlling and terminating sessions. Therefore, an MGCP protocol is used to set up, maintain and end calls between multiple points.