| 摘要 |
Remote disconnection devices are needed for being able to determine at the interface between the telephone network of one operator and the network of another operator the part of the coupled networks in which a fault has occurred, that is to say to separate the networks from one another with respect to direct voltage for measuring purposes. Remote disconnection devices based on TRIACs and MOSFETs are known where a uniform switching threshold is used. If controlled silicon rectifiers are used as electronic switches, the switches are connected to one another by a switching element in order to be able to transmit dialling pulses from the telephone to the exchange and to use switches with tolerant control connections. According to the invention, the use of self-inhibiting MOSFETs of the enrichment type provides for a high turn-on threshold and a low turn-off threshold so that the usual measuring method of lowering voltage can be used. It is also possible to make the turn-on threshold dependent on the polarity of the voltage. <IMAGE> |
