package Commands is

    Any_Session : constant String := "@";

    Whoever_Is_Phoning : constant String := "@";

    procedure Phone (User : String;
                     Session : String := Commands.Any_Session;
                     Wait : Duration := 30.0);

    procedure Answer (User : String := Commands.Whoever_Is_Phoning;
                      Session : String := Commands.Any_Session);
end Commands;