Abstract: A digital demodulation apparatus which has a detector (11) for receiving transmission signals (S.sub.in) modulated under a multivalue quadrature amplitude modulation method in accordance with a honeycomb signal structure point arrangement. The detector produces I channel and Q channel demodulation signals. The apparatus also includes a discriminator (13) which converts the analog demodulation signals (Sa) to digital demodulation signals (Sd), a memory (21) which successively receives said digital demodulation signals (Sd) and reproduces corresponding original data. The read only memory (21) stores data representatives of the honeycomb signal structure point arrangement, and stores polarity bits (P) and error bits (.epsilon.) of the signal points.

Abstract: The present invention relates to a radio transmission system. The system includes a transversal type automatic equalizer which controls tap weight based on bit error rate (BER) from a pseudo error pulse. In the equalizer, the threshold value (BER1) which defines the mode change for tap weighting control from normal to reset is different from the threshold value (BER2) from reset to normal. Therefore, the mode change is carried out by a simple circuit properly and stably.