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.
This is a way of communicating on the half-duplex communication line, includes receiving and transmitting devices (walkie-talkie) by the way of pressing the button for switching to the voice mode or transition to the listening mode. It works as a radio speaker; one can talk by pressing the button and can listen to a voice message by releasing the button.