n 1 if none of the above conditions are met that is the comparisons do not produce a definitive result decesion circuit 306 determines that the jbtsc transmission is in mono mode decision n mono that is the audio transmission is in mono mode when the amplitude of stereo filtered signal 320 is lower than a lower threshold times the amplitude of dual mono filtered signal 324 and the amplitude of dual mono filtered signal 324 is lower than the lower threshold times the amplitude of stereo filtered signal 320 fig6 is a timing diagram of mode determination signal 402 stereo filtered signal 320 and dual mono filtered signal 324 the values shown are in accordance with the embodiment described above in fig6 a higher value for mode determination in signal 402 corresponds to stereo mode similarly a lower value for mode determination in signal 402 corresponds to dual mono mode as shown in fig6 when stereo filtered signal 320 has an amplitude that is at least three times larger than the amplitude of dual mono filtered signal 324 mode determination signal 402 corresponds to stereo mode as the amplitude of stereo filtered signal 320 begins to decrease and the amplitude of dual mono filtered signal 324 begins to increase mode determination signal 402 does not immediately change during this transition period the comparison made in step 512 of method 500 applies since the amplitude of stereo filtered signal.