Abstract: A method for operating a data network, which includes at least one transmission link, defined by a transmitter and a receiver, wherein in test mode the actual level reserve in the direction of the sensitivity limit, thus between the actual transmitting power of the transmitter and the actual sensitivity limit of the receiver, is determined for at least one transmission link. To better utilize the transmitting capacity of the data network, in test mode, the actual level reserve in the direction of the overload limit, thus between the actual transmitting power of the transmitter and the actual overload limit of the receiver, is also determined for the at least one transmission link.

Abstract: A method for checking a ring optical network line for data transmission between a plurality of network subscribers in a motor vehicle, wherein one network subscribers carries out a master function, wherein, apart from the optical network line, there is a further communication line which has a star structure. The network subscribers having the master function is arranged in the centre of the star structure and is connected directly via the communication line to every other network subscribers. The optical network line is checked by the network subscriber having the master function outputting a start signal to the individual network subscribers. The individual network subscribers acknowledge the start signal for the network subscribers the master function via the communication line. After the start signal, the network subscriber having the master function outputs an initialization signal via the optical network line.

Abstract: In a method for determining the failure probability of a data network which has at least one transmitter, a transmission medium, components which attenuate and/or amplify the power, and at least one receiver, the data network is subdivided into individual point-to-point connecting paths, and a failure probability is determined separately for each point-to-point connecting path. The total failure probability of the data network is determined as the sum of the individual probabilities of the individual point-to-point connecting paths, minus the probability that two or more point-to-point connecting paths will fail simultaneously.

Abstract: A method for operating a data network, which includes at least one transmission link, defined by a transmitter and a receiver, wherein in test mode the actual level reserve in the direction of the sensitivity limit, thus between the actual transmitting power of the transmitter and the actual sensitivity limit of the receiver, is determined for at least one transmission link. To better utilize the transmitting capacity of the data network, in test mode, the actual level reserve in the direction of the overload limit, thus between the actual transmitting power of the transmitter and the actual overload limit of the receiver, is also determined for the at least one transmission link.