A social care alarm system , comprising: at least one client terminal unit configured to be installed in a dwelling of a client; and a monitoring centre remotely coupled to the client terminal unit by a set of data carriers over one or more communications networks; wherein the client terminal is operable to communicate using a selected data carrier in the set of data carriers over a selected communication network of the one or more communications networks, and configured to send status messages at predetermined intervals to the monitoring centre using the selected data carrier over the selected communications network; characterised in that: the client terminal unit is operable to communicate with the monitoring centre in a master-slave communication session including a connection phase and disconnection phase , the client terminal unit is configured to receive request messages from the monitoring centre during the master-slave communication session, to raise an alarm event with the monitoring centre by sending a response message during the master-slave communication session, and to support a voice call between the client terminal unit and the monitoring centre in response to the alarm event; and the status messages are sessionless, being sent by the client terminal unit without forming the master-slave communication session with the monitoring centre . at least one client terminal unit configured to be installed in a dwelling of a client; and a monitoring centre remotely coupled to the client terminal unit by a set of data carriers over one or more communications networks; wherein the client terminal is operable to communicate using a selected data carrier in the set of data carriers over a selected communication network of the one or more communications networks, and configured to send status messages at predetermined intervals to the monitoring centre using the selected data carrier over the selected communications network; characterised in that: the client terminal unit is operable to communicate with the monitoring centre in a master-slave communication session including a connection phase and disconnection phase , the client terminal unit is configured to receive request messages from the monitoring centre during the master-slave communication session, to raise an alarm event with the monitoring centre by sending a response message during the master-slave communication session, and to support a voice call between the client terminal unit and the monitoring centre in response to the alarm event; and the status messages are sessionless, being sent by the client terminal unit without forming the master-slave communication session with the monitoring centre . the client terminal unit is operable to communicate with the monitoring centre in a master-slave communication session including a connection phase and disconnection phase , the client terminal unit is configured to receive request messages from the monitoring centre during the master-slave communication session, to raise an alarm event with the monitoring centre by sending a response message during the master-slave communication session, and to support a voice call between the client terminal unit and the monitoring centre in response to the alarm event; and the status messages are sessionless, being sent by the client terminal unit without forming the master-slave communication session with the monitoring centre . <EOS>