def rssi # optional
      @o_dev[I_DEVICE]['RSSI']
    rescue DBus::Error => e
      case e.name
      when E_INVALID_ARGS then raise NotSupported
      else raise ScriptError
      end
    end
def rssi # optional
      @o_dev[I_DEVICE]['RSSI']
    rescue DBus::Error => e
      case e.name
      when E_INVALID_ARGS then raise NotSupported
      else raise ScriptError
      end
    end
Received Signal Strength Indicator of the remote
 device (inquiry or advertising).
 @return [Integer]