| 摘要 |
PURPOSE:To eliminate adverse influences arising from a monitor signal by stopping the output of the monitor signal when the monitor signal does not show a normal monitor level since a power supply voltage shared by a subscriber equipment and a monitor circuit is lowered. CONSTITUTION:This circuit is provided with a power supply voltage abnormality detection circuit 2 for outputting an abnormality detecting signal VAB to be an active level when a power supply voltage Vbb shared by the subscriber equipment and the monitor circuit gets out of a prescribed voltage range. Then, a function to stop the output of the monitor signal corresponding to the abnormality detecting signal VAB at the active level is added to a comparator 13 of a hook monitor circuit 1. |
