 Smart antennas remove the burden of positioning the antenna for digital TVs and can make the tuning process easier than it was with analog television.There are two basic modes of operation for a CEA-909 antenna, mode A and mode B. Mode A allows for communication only from the tuner to the antenna and Mode B allows for bidirectional communication.A 14-bit pulse-width modulation data stream is sent to the antenna and if the antenna is mode B a 10-bit data stream is sent back.