A method for initializing a network for data transmission between a plurality of subscribers being connected to one another in ring-like fashion, includes sending a clock signal through the network in a continuous data stream, originating at a network position. In each subscriber, a process of locking onto the clock frequency is started after reception of the data stream, and the data stream is forwarded to the next subscribers in succession after locking on is completed. In order to speed up the initializing process, the arriving data stream is split into two identical streams at each subscriber, as long as it has not yet locked on. One of the streams is used for the locking-on process and the other of the streams is immediately forwarded to the next subscriber.

A low speed channel bypass apparatus is described for reprovisioning the time slot multiplexer associated with an add/drop multiplexer so as to insure that particular low speed channel(s) within a high speed channel are passed through the add/drop multiplexer via the time slot multiplexer when the operation of an associated network controller is determined to be faulty. The low speed channel bypass apparatus is particularly directed for use with a high speed channel conforming to the synchronous optical network communication standard (SONET). A watchdog timer is used to monitor the performance of the network controller. The watchdog timer when timed out not only prevents further operation of the network controller, but instructs an associated reprovisioning apparatus to instruct the time slot multiplexer to connect through selected channel(s) from the east high speed interface to the west high speed interface.

To reduce signal rate in connection with a code error detecting circuit for handling transmitted signals encoded in accordance with an mB1C code, the transmitted signal is divided into a plurality of p parallel signals each of which has a bit rate 1/p of the bit rate of the input signal. The number of parallel signals p is restricted to meet the condition that the product of (m+1).times.p is equal to the smallest number which is a multiple of both (m+1) and p. The parallel secondary signals are delayed relatively to one another in a manner which guarantees that the error codes contained in them coincide. The secondary signals are then exclusive ORed with one another and the exclusive ORed output is directed to an error detection circuit to detect whether an error has occurred in the input signal.

A multi-ring network structured by connecting a plurality of rings having different speeds. The multi-ring network includes a first ring structured by connecting a plurality of first nodes by a pair of ring-formed first transmission lines, a second ring structured by connecting a plurality of second nodes by a pair of ring-formed second transmission lines, and a third node for connecting the first ring and the second ring. The first transmission line has a first transmission speed and the second transmission line has a second transmission speed lower than the first transmission speed. The third node has a demultiplexer for deriving a plurality of handling group data by time division demultiplexing data having the first transmission speed, conversion means for converting data having the second transmission speed into handling group data, a plurality of highways adapted to transmit the handling group data, and a multiplexer for time division multiplexing the handling group data and outputting the multiplex data to the first transmission line. In the third node, data are handled for each handling group data as a unit and the selected handling group data is connected to the first or second ring.

A network system for transmitting vehicle data has a bidirectional multidrop ring in which data communication between data transmitting nodes and corresponding data receiving nodes is carried out even if a breakage or some other trouble occurs at a portion of the multidrop ring. This system ensures safe and reliable control of various vehicle loads for a long period of time. At least one multidrop bus or at least one further bidirectional multidrop ring may be electrically connected to the first-mentioned bidirectional multidrop ring, thereby widening the applicability of the system to the control of vehicle loads.