When Conference Calling is invoked, conference resources (e.g.a "bridge") are allocated to the served user, and any calls indicated by the service request are added to the conference. Once a conference is active, parties may be added, dropped, isolated (i.e. prevented from communicating with the conference), reattached, or split (i.e. removed from the conference but remain connected to the conference controller). The controller can place his connection to the conference on hold, retrieve the conference, end the conference, or disconnect himself from the conference.