| 摘要 |
PURPOSE:To improve noise characteristic for the idle circuit by detecting the idle circuit state on a basis of the code output of a PCM encoder and outputting an idle circuit fixed pattern for the idle circuit instead of the code output. CONSTITUTION:An 8-bit PCM code is inputted to a register 1 for every one sample. The difference between the current PCM code and the PCM code one sample period before is operated in respect to a code part 2 and a step part 4 by a subtractor 5 and a register 5 for delay of one sample period. This difference is compared with a threshold input 14 from a pattern generator 10 in a comparator 7; and if the difference is lower than the threshold, a signal 16 is outputted. A code part 3 of the PCM code and a pattern 13 of the first segment from the pattern generator 10 are compared with each other in a coincidence detecting circuit 8; and if they coincide with each other, a signal is outputted. The output of an AND between the signal 16 and the output of the coincidence detecting circuit 8 is inputted to a discriminating circuit 11. The discriminating circuit 11 discriminates the idle circuit when N-number of an AND outputs are continuous, and an idle circuit pattern 15 from the pattern generator 10 is selected and outputted instead of the PCM code. |
