Abstract: A vital serial link for linking a plurality of data processors which act on information communicated in the form of link information signals, into a vital serial communications network, including at least two vital serial controllers, one for each direction of transmission, in the vital serial link, each controller including a means for storing a plurality of link parameters, each of the link parameters including a numerical relationship indicating that a specified first processor originated a signal and that a designated second processor is to receive said signal, a unique numerical relationship being provided for each possible combination of signal originating processor and signal receiving processor; whereby, upon receipt of a signal, the signal receiving processor can discriminate signals sent to the receiving processor, and determine which processor in said network was the signal originating processor.