In the event of a fire or disaster alarm, an immediate mass alerting is required. With MobiCall, the existing ICT infrastructure can be used so that existing telephones and computers are available for audible and visual alarm signalling. IP loudspeakers or central Public Address Systems can be connected together so that the proper announcements are played for instance in halls and corridor areas. A sectoral alert can be configured according to fire compartments or floors and adapted to the local circumstances. The acting people can be coordinated by means of an automatic initiated telephone conference. All operations are logged in detail.