| 摘要 |
PURPOSE:To ensure a monitor for the normal talking state with a simple constitution, by producing an alarm in case a vocal sound is detected and the signal frequency is outside the talking band. CONSTITUTION:The coder monitor circuit 1 comprises the time slot selection circuit 6, the zero-cross number conter circuit 7, the level detecting circuit 8 and the coder alarm producing circuit 11 each. The circuit 18 examines the 1st (code bit), 2nd (MSB) and 3rd bits within a time slot, and the circuit 7 counts the zero-cross number with a notice given to the replacement of the 1st bit. In case the input of a vocal sound is decided by the circuit 8 with the zero-cross number existing outside the fixed range, the fault of the coder is decided by the coder alarm generating circuit 9 to produce an alarm. |
