| 摘要 |
PURPOSE:To prevent the occurrence of howling caused by the change of circuit condition due to the withdrawal of a participant by detecting the AC loop current of each participating subscriber and automatically reducing the signal level of the participant when his loop current stopped. CONSTITUTION:Input voice signal line 101 is connected to a non-linear/linear conversion circuit 11, and its output is connected to a silent insertion circuit 12. On the other hand, a AC loop current existence/non-existence signal line 102 is connected to an AC current existence/non-existence direction circuit 13, and its output controls the action of the silent insertion circuit 12. The output of silent insertion circuit 12 is connected to an adder circuit 14 and a memory 17. The adder circuit 14 adds the output of silent insertion circuit 12 and the output of register 16a, and its result is recorded at 16b again. The final result of addition recorded in register 16 is then recorded on register 16b. Furthermore, a subtracter circuit 15 subtracts the output of memory 17 from the output of register 16b, then connected to output voice signal line 103 through the linear/non-linear conversion circuit 18. |
