| 摘要 |
<p>A device is proposed which is to be used in telephone systems for cancelling echoes which are generated at the transition of four wire lines (3, 5) to two wire lines (1). Therefor a signal processor and a microprocessor (31) are provided, where the signal processor is rapid and handles the direct signal processing. It contains a double talk detector (25) and a calculating device (17) using an adaptive algorithm. The microprocessor (31) monitors the echo cancelling and sets the stepsize of the adaption. A direct path (27, 29) is arranged between the detection device (25) and the calculating device (17) in such a way, that when a double talk state is detected, the adaption is immediately and completely shut off inside the calculating device (17). The microprocessor (31), which only periodically monitors the detection device (25), sets the stepsize of the adaption at a reduced value, when said microprocessor (31) in a periodical check will find, that the double talk state is present. The adaption having a reduced stepsize is maintained during a long predetermined time period, during which the direct path between the detection device (25) and the calculating device (17) is blocked.</p> |
