| 摘要 |
PURPOSE:To eliminate the need for designation of the transmission speed by identifying the transmission speed depending on the difference of phase change at each modulation time slot during a training signal period. CONSTITUTION:The circuit is so constituted that a received demodulation complex signal 100 and a signal 101 giving two-modulation time slot's share to the signal 100 are added and whether the transmission speed of the reception signal is 2,400bps or 1,200bps is identified automatically at the beginning of the turn-on sequence by using the power of an added complex output 102 as the result of the said addition. In other words, a logical output 104 being an output of a comparator circuit 53 is at high level in case of 2,400bps and at a low level in case of 1,200bps by setting properly the threshold value of the comparator circuit 53. Thus, the transmission speed of the reception signal is decided by using a deciding output 120 so as to set the speed of the demodulation cicuit corresponding to the transmission speed before a user data reaches. |
