| 摘要 |
<p>PURPOSE:To provide a terminal equipment monitoring system which can easily increase a terminal equipment and also to simplify the constitution of a monitoring device. CONSTITUTION:A terminal equipment monitoring circuit includes a phase comparator 15 which produces a signal that has the same frequency as the input monitoring signal and also has a proper level, a DC amplifier 16, a voltage control oscillator 17, and a level control amplifier 18. The amplifier 18 is connected to an adder 22 as well as to a phase controller 21 which synthesizes the output of the amplifier 18 with the input monitoring signal in synchronization via a relay switch that outputs an input signal as it is when a terminal equipment is normally working. Furthermore a comparator 29 is added to the terminal equipment monitoring circuit to detect the level of the input monitoring signal, together with a fault deciding part 30 which decides the operating states of all terminal equipments based on the output of the comparator 29.</p> |
