A detection circuit monitors a hardware-level signal received from a remote device for voltage transitions indicating that the remote device is connected to a network cable. If the detection circuit does not sense voltage transitions in the hardware-level signal, it is presumed that the remote device has been unplugged from the network cable and the detection circuit generates an immediate or delayed control signal to terminate supplying power through the network cable. In one application, the network cable supports communications based on a layered network protocol such as Ethernet and the detection circuit is employed at physical layer associated with the layered network protocol. Based on this topology, power supplied through the network cable can be terminated on the order of milliseconds instead of 1.5 seconds according to conventional methods.