在配置设备的网络22与主干网络21和两个位置连接的，通常与通信地连接所述设备11-1和开关单元2-2，该装置11-4和开关装置2-1中 切断通信。 设备11-1监视开关单元2-2的链路状态，设备11-4询问所述链路状态设备11-1。 设备11-4中，当设备11-1和开关单元2-2不可通信地连接，或者，如果不能经由所述设备网络22，开关设备2与设备11-1进行通信 释放1之间的中断状态。

In the configuration device network 22 is connected by a backbone network 21 and two positions, usually together communicatively connecting the equipment 11-1 and the switch device 2-2, the device 11-4 and the switch devices 2-1 to cut off the communication. Equipment 11-1 monitors the link status of the switch device 2-2, device 11-4 inquires the link state to the device 11-1. Equipment 11-4, when the equipment 11-1 and the switch device 2-2 is not communicatively connected, or, if unable to communicate with the device 11-1 via the device network 22, switching device 2 to release the cut-off state between the 1.