An apparatus includes first and second circuits that transmit and receive information to and from each other through first paths, where each of the first and second circuits includes second paths respectively coupled to the first paths, and matrix switches that are provided across the second paths and switch a transmission path of information transmitted to any one of the second paths. Upon detecting an error in the second paths, the apparatus conducts a loop-back test in which each matrix switch is switched to a loop-back state in which information to be transmitted to the second path in which the error has been detected, is looped back. Upon detecting an error in the loop-back test, the apparatus switches the matrix switches to a bypass state in which the second path in which the error is detected is bypassed to another one of the second paths to continue the loop-back test.