In a magnetic disk device, a magnetic circuit drives an actuator carrying a magnetic head, so that the magnetic head is moved to a target track on a surface of a magnetic disk. In a preferred manner, the common wall has a tiered configuration. The reflected radiation can then be used to estimate a position of the body portion of the user. The current position of each train is compared to its planned schedule online to provide immediate information to the dispatcher to determine whether a corrective action is necessary. The, device is further configured to report to at least one other device at least one metric related to an availability of each of the one or more selected communications channels for communications.