| 摘要 |
<p>PROBLEM TO BE SOLVED: To discriminate a speech at a remote end of a transmission line from an echo of a talker of a telephone terminal quickly with reliability. SOLUTION: A signal from a remote talker is received by a telephone terminal via a reception line 2, a signal or a surrounding noise signal of the local talker at the telephone terminal is sent to the remote talker through a transmission line 1 and a mean value of a sampled signal sent from the telephone terminal and a mean value of the received sample signal are decided by averaging devices 4, 5. Then the mean value of the transmission signal is divided by the mean value of the reception signal at a divider 6 to form a quotient representing a short time mean value of the attenuation of the transmission line and an averaging device 9 decides a mean value of quotients representing a long time mean value of the attenuation of the transmission line and a difference between the long time mean value and the short time mean value of the attenuation is calculated and it is compared with a threshold level at a comparator 8, and when the difference is smaller than the threshold level, it is discriminated that the reception signal comes from a line echo and when the difference is larger than the threshold level, it is discriminated that the reception signal comes from the remote talker.</p> |
