Abstract: A central control unit and a plurality of data processing units are connected to a bus line and are provided to control restraint devices. The central control unit sends query signals or control signals in the form of data telegrams to all or certain individual data processing units and the data processing units send response signals back to the central control unit in response to certain query signals or control signals. To permit a reliable allocation of query signals and control signals to data processing units and reliable acquisition of monitoring data of data processing units and their restraint devices, the query signals or control signals and the response signals are data telegrams, all of which have the same frame structure, having a first region with n control bits, a second region with m information bits and a third region with p check bits.