Network connected device protection

摘要

A network protection method and apparatus are disclosed for alerting an operator when a terminal device is disconnected from the network. A network controller adapter is connected to a network control computer. The network controller periodically stops normal data communication and scans some or all of the network ports to ascertain the present and absent status of a terminal device at each port. Status is detected by passing a current through a port and measuring the feedback voltage. If the status changes between scans, an operator is alerted by sounding an alarm at the network control computer or by other steps such as dialing a telephone number and transmitting a stored message or by transmitting an alarm message over the network to one of the terminal devices such as a personal computer.