| 摘要 |
PURPOSE:To prevent the generation of a fault of an adaptive differential coder or a large DC signal and oscillation to the output signal of an adaptive differential decoder, by deciding whether the result of coding has the same value at eath time. CONSTITUTION:A quantization step is supplied to a deciding circuit 505 from an adverse quantitizer 162. When it is decided that the value of the quantization step is equal to a level which is impossible to obtain in the normal state, ''0'' is delivered to a signal line 551. Therefore the coding result U1 is set at the same value at each time, and the quantization step is set at a level which is impossible to obtain in the normal state. In such a state, the output of a decoder is set at 0. Otherwise a decoding signal xj is delivered. In such a way, the output of a decoder is never turned into an extremely large DC signal or an oscillating signal even though a coder has no working or a signal line is interrupted. |
