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21. 发明授权

US4709386A Subscriber line monitoring circuit 失效
标题翻译：用户线路监控电路
公开(公告)号：US4709386A
公开(公告)日：1987-11-24
申请号：US862042
申请日：1986-05-12
申请人： Toshimitsu Shimizu
发明人： Toshimitsu Shimizu
IPC分类号： G01R27/26 , G01R31/02 , H04M3/30 , H04B3/46
CPC分类号： H04M3/30 , G01R31/021 , H04M3/301
摘要： There is disclosed a circuit for monitoring a capacity of a subscriber line to which a capacitor equivalently representative of a telephone set is connected. This monitoring circuit has a test sequence for the subscriber line capacity. The test sequence comprises a first step to connect the subscriber line to a test circuit, and second step to apply a backward voltage to the subscriber line, thereby to discharge an electric charge stored in the equivalent capacitor. The test sequence further comprises a third step to apply a forward voltage to the subscriber line through a reference capacitor, thereby to charge the equivalent capacitor to evaluate the capacity value of the equivalent capacitor on the basis of a voltage appearing across the equivalent capacitor, thus to effect a capacitive test of the subscriber line. Accordingly, where the telephone set includes a diode bridge in an interface of the subscriber line, diodes constituting the diode bridge can become conductive so as to enable the formation of a current charging path at the time of the execution of the third step. Thus, this makes it possible to conduct a capacitive test of not only ordinary telephone set but also telephone sets of the type including the diode bridge in its subscriber line interface.
摘要翻译：公开了一种用于监视与电话机等效地代表电容器的用户线的容量相关联的电路。该监控电路具有用户线容量的测试顺序。测试序列包括将用户线路连接到测试电路的第一步骤，以及向用户线路施加反向电压的第二步骤，从而放电存储在等效电容器中的电荷。测试序列还包括通过参考电容器向用户线路施加正向电压的第三步骤，从而根据出现在等效电容器两端的电压来对等效电容器充电以评估等效电容器的容量值，从而以实现用户线的电容测试。因此，在电话机在用户线的接口中包括二极管桥的情况下，构成二极管电桥的二极管可以变为导通状态，以便在执行第三步时能够形成充电路径。因此，这使得可以进行不仅普通电话机的电容测试，而且还可以在其用户线路接口中进行包括二极管桥的类型的电话机。

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