| 摘要 |
PURPOSE:To prevent an exchange from terminating its call due to mis-information during communication by outputting an output signal of a detector or a waveform shaping circuit as a signaling signal only when the output signal is a signal allowed as the signaling signal. CONSTITUTION:When the signaling signal by the interruption of a prescribed frequency is inputted to a BPF 2 from an input terminal 1, the signal is converted into a DC pulse and inputted to a waveform shaping circuit 4, where the signal is waveform-shaped and inputted to a comparator 6. The comparator 6 compares the signal with a preset reference level and only when the level is larger than the reference level, the control signal being at a prescribed level is outputted. When the level is larger than the reference level, the gate circuit 7 sends the output signal of the waveform shaping circuit 4 to an output terminal 5 and when the level is smaller, the transmission to the output terminal 5 is blocked. Thus, the output signal of the waveform shaping circuit 4 becomes the signaling signal equal to the initial signaling signal and the result is outputted from the output terminal 5. |
