| 摘要 |
PURPOSE:To attain excellent echo cancellation by applying stop control to an echo canceller when a level of a PCM signal sent from a digital exchange is low and a value of a least significant bit is unchanged to clear the internal parameter. CONSTITUTION:The level of a PCM signal sent from a digital exchange 10 and the value of a least significant bit of the signal are monitored by a monitoring means 18. When a clearing means 20 confirms from the output of the monitor means 18 that the level of the PCM signal sent from the digital exchange 10 is low and the value of the least significant bit in the signal is unchanged, the clearing means 20 applies stop control to an echo canceller 16 and the internal parameter of the echo canceller 16 is cleared. Thus, the production of distortion of a tone signal or the like is prevented and the echo cancellation at the connection of a telephone set is improved in an excellent manner. |
