COMMUNICATION SYSTEM, MASTER STATION DEVICE, AND METHOD FOR DETECTING OPERATION STATE OF SLAVE STATION DEVICE

PROBLEM TO BE SOLVED: To quickly detect whether a slave station device is in a malfunction state such as the slave station device transmits an uplink signal in a time other than the time allocated to its own device.SOLUTION: A communication device according to the invention, in a communication system in which a master station device and a plurality of slave station devices are connected via transmission paths, comprises: signal transmission means to which a transmission permission signal and a signal to be transmitted are input and which outputs an uplink signal; designating means for designating a test signal and a transmission time of the test signal; instruction means for instructing a slave station device such that the test signal designated by the designating means is supplied to the signal transmission means and the transmission permission signal is not supplied to the signal transmission means at the designated time; signal receiving means for receiving a signal transmitted by the signal transmission means; and operation state detection means for detecting the operation state of a slave station device based on a reception result by the signal receiving means.