| 摘要 |
PURPOSE:To eliminate noises due to abnormal synchronism occurring when a device is troubled, by detecting the abnormal synchronism of multiplexed PCM voice signals by the checking circuit of a demodulator, and by fixing voice signal data as data with a no-signal level when the abnormal synchronism is found. CONSTITUTION:Multiplex PCM voice signals selected by a changeover circuit are sent to a clock generating circuit 4, and a clock regenerated by the circuit is frequency-divided by a counter circuit 18, whose output is sent to a synchronism checking circuit 19. A voice signal sent to a shift register 5, on the other hand, is sent to the circuit 19 via a synchronous separating circuit 6. Then, the detected synchronizing signal from the circuit 6 and the clock from the circuit 18 are compared mutually by the synchronism checking circuit in terms of timing to check the existence of abnormal synchronism. When they are not synchronized with each other, a switching control signal Se is sent to a data switching circuit 7 to select no-sound level data, so that noises due to abnormal synchronism occurring when a device is troubled are prevented. |
