Abstract: The present invention provides a relay-based foolproof circuit for over-voltage protection, which is electrically connected between a plug and an electric device, and includes a relay having at least one magnetic core, a coil wound around the magnetic core and two reed switches each having a reed and being normally in a closed state because of the elastic effect of its reed. The relay-based foolproof circuit is able to provide AC power of a first specification (e.g., 110 V AC power) received from the plug to the electric device. However, when AC power of a second specification (e.g., 220 V AC power) greater than the first specification flows through the coil, the coil causes the magnetic core to generate a magnetic force great enough to drive the two reed switches into an open state for stopping the AC power of the second specification from being provided to the electric device.

Abstract: The present invention provides a relay-based foolproof circuit for over-voltage protection, which is electrically connected between a plug and an electric device, and includes a relay having at least one magnetic core, a coil wound around the magnetic core and two reed switches each having a reed and being normally in a closed state because of the elastic effect of its reed. The relay-based foolproof circuit is able to provide AC power of a first specification (e.g., 110 V AC power) received from the plug to the electric device. However, when AC power of a second specification (e.g., 220 V AC power) greater than the first specification flows through the coil, the coil causes the magnetic core to generate a magnetic force great enough to drive the two reed switches into an open state for stopping the AC power of the second specification from being provided to the electric device.

Abstract: The present invention relates to an environment monitoring system for monitoring environment for installing community Ethernet switch, which comprises an Ethernet switch installed in a panel room at a community and an environment monitoring device coupled between the Ethernet switch and a central office so that a packet transmission can be effected between the central office and a plurality of end users through the Ethernet switch and the information monitored by the environment monitoring device can be transmitted to the central office enabling the central office to monitor the panel room through the environment monitoring device and perform a real time monitoring on the environment for installing the Ethernet switch at a remote place.

Abstract: A dual speed hub includes a CPU, two hubs of different transmission speeds, two MACs (media access controls), and a switch, wherein the CPU periodically sends a test packet in proper order through one MAC, one hub, the switch and the other hub to the other MAC, then checks the receiving condition and the content of the returned test packet, then determines the normality of the function of the switch subject to the receiving condition and the content of the returned test packet, and then provides a warning signal to a network management system when the switch is judged abnormal, informing the network manager to repair the switch.