A packer assembly for a blowout preventer for sealing a wellbore is provided. The mixing device may be formed as a Venturi nozzle, in which the gas flow and the combustion air flow are mixed, wherein the reference pressure for the sensor is a device in which the reference pressure prevails, and the device is connected via a connecting line to the Venturi nozzle downstream of the mixing region of the Venturi nozzle. To execute enlargement processing, the image data is compressed and stored, then enlarged; to execute reduction processing, the image data is reduced, then compressed and stored, whereby the memory resources can be used effectively. Finally, a first packet from the first codeword is transmitted using a first transmission channel indicated by the first process identity, and a second packet is transmitted from the second codeword using a second transmission channel indicated by the second process identity.