Abstract: In a network, such as a large telecommunication switch, intended for the processing of information in different stations and for transmitting information between the stations, centrally located circuits are provided, which independently generate clock signals containing both a system clock rate and a frame synchronizing rate. These clock signals are transmitted on several, in the preferred case three, different transmission lines to a station where a multiplexor makes a selection of a clock signal as controlled by evaluation circuits containing circuits for determining errors in the received clock signals and also containing a state machine. The multiplexor selects periodically and repeatedly all the time a new clock signal in a cyclical pattern, which is accomplished by temporary, very short errors that are introduced when generating the issued clock signals.

Abstract: A functional entity in a digital switch is triplicated in planes operating in parallel. From each plane, a respective passing data flow is spread to parallel planes. A majority vote function receives the data flows of the planes and compares these on a bit level for creating a majority voted data flow. A plane condition sensing function indicates whether links of the planes have meaningful information and synchronism, and emits, as a result, a link condition indicating signal for each plane. A priority select function is connected for receiving the majority voted data flow and the link condition indicating signals. If the link condition indicating signals indicate a fault condition, the priority select function lets the majority voted data flow through as an outgoing data flow from the functional entity.

Abstract: In a network, such as a large telecommunication switch, intended for the processing of information in different stations and for transmitting information between the stations, circuits are provided which generate independently composite clock signals containing both a clocking rate and a frame synchronizing rate. These clock signals are transmitted on three different transmission lines in parallel and independently to a station, where some kind of information processing is made in redundant planes. In the station all incoming clock signals are fed to each one of three independently operating selector units in which a choice of a clock signal is made for obtaining a clock signal to be used in the three redundant planes arranged in parallel to each other and operating independently of each other, in the station.