Method and a device for supervising and testing majority voting

A device for testing and supervising majority votes in a multiplane unit in a digital time selector, said unit including essentially identical equipment in each of at least three planes (A,B,C) working in parallel, means for distributing to the parallel planes a dataflow received by said unit, comprising:

• means for passing said data flow through the equipment in each panel;
• means for delivering an outgoing data streams on an outgoing line from the respective planes, said lines each being connected to an input of a majority vote circuit including means for comparing these outgoing data streams to each other;
• means for delivering from the unit a majority voted outgoing dataflow based upon the comparison;
• a comparison and supervision circuit having inputs connected to each of the outgoing lines from the multiplane unit and to a line from the output of the majority vote circuit, respectively, and having means for testing and supervising the majority vote by comparing the received data streams with the majority voted data flow;
• means for deliberately introducing an error into the data streams received by the majority vote circuit from the multiplane unit, including means for cyclically introducing the error into the planes of the multiplane unit in accordance with a predetermined pattern;
• and
• means for emitting an alarm if an error is found in any of said data streams;
• means for identifying an expected alarm, which has been caused by an error introduced in accordance with the predetermined pattern, based upon knowledge of the predetermined pattern, in order to distinguish which results from errors not introduced in accordance with the pattern.