Patent ID: 8299932

Claim:
A closed-loop monitoring system comprising: a host device; and a plurality of monitoring devices coupled in series to said host device through a single transmission line such that said host device, said monitoring devices and said transmission line constitute a closed-loop structure; wherein said host device has a coupling side coupled to opposite ends of said transmission line, and includes a signal generating unit coupled to said coupling side, operable to generate encoded signals and outputting the encoded signals through said coupling side to said transmission line; each of said monitoring devices having an input side coupled to said transmission line and including a signal current generating element coupled across said input side such that the encoded signals pass through said signal current generating element, a current inducting generating unit disposed adjacent to said signal current generating element for generating induced encoded signals when the encoded signals pass through said signal current generating element, a control unit coupled to said current inducting generating unit, receiving the induced encoded signals from said current inducting generating unit, identifying a monitoring signal from the induced encoded signals received thereby, and outputting the monitoring signal, and a detecting unit adapted to be coupled to a plurality of first electronic devices, coupled to said control unit for receiving the monitoring signal therefrom, detecting, in response to the monitoring signal received thereby, whether each of the first electronic devices is activated or deactivated, generating a reply signal associated with states of the first electronic devices based on a detection result made thereby, and transmitting the reply signal to said transmission line; and said host device further including a processing unit coupled to said coupling side and receiving the reply signal from each of said monitoring devices through said transmission line and said coupling side such that said processing unit obtains state information associated with the first electronic devices coupled to each of said monitoring devices.