A communications system having a pre-defined calling group with a plurality of members is disclosed. A plurality of personal communication devices (PCDs) each have a system ID and a group ID, and each member of the group is assigned one of the PCDs. The system ID and the group ID both have a predetermined characteristic, where each system ID has a first variation thereof and each group ID has a second variation. A first group member having a first PCD contacts a second member having a second PCD by entering into the first PCD the second PCD group ID. The first PCD transmits the first PCD system ID and the second PCD group ID to a communications switch. Based on the first PCD system ID, the communications switch locates a record for the first PCD in a switch database and determines therefrom that the first PCD can contact the second PCD by way of the second PCD group ID. A group database in switchable communication with the communications switch has the system ID and group ID for each group member PCD. The communications switch forwards the contact and the second PCD group ID to the group database for further processing. The group database determines that the second PCD group ID is located therein, locates the second PCD system ID based on the second PCD group ID, and forwards the attempted contact and the second PCD system ID to an appropriate communications switch for further processing.

 
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> Method of capturing constant echo path information in a full duplex speakerphone using default coefficients

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