A data processing apparatus is provided having a plurality of processing circuits each having access to a memory. The controller compares a second position of the windowpane derived from a second signal generated by the transducer when the supply voltage for the motor is restored to the predetermined level or higher with the first position of the windowpane stored in the memory. The client connects to the switch using multiple bandwidth connections. When the inferior node receives a timing message, said inferior node extracts the local time of the superior node, which is contained in said timing message and adds the minimum propagation time thereto, in order to generate a reference time.