Patent ID: 7209809

Claim:
A method comprising: generating synchronous digital control data at a pair of computer systems of a plurality of redundant pairs of computer systems, wherein the digital control data is one of discrete or continuous variable data; sending the generated synchronous digital control data to a plurality of line replaceable units; selecting the digital control data of one of the computer systems of the pair of the plurality of redundant pairs of computer systems; converting the selected digital control data into an analog signal; sending the analog signal to a corresponding actuator; and checking validity of each redundant pair of computer systems, wherein checking the validity includes: determining a freshness invalid signal; and determining if an error condition exists based on the corresponding digital control data and the freshness invalid signal, and wherein determining if an error condition exists includes: if a difference between the digital control data of each computer system of a pair is greater than a threshold value, adding a first constant value to an error value; if the difference between the digital control data from the computer systems of a pair is less than the first threshold value, subtracting a second constant value from the error value; if the error value is greater than a second threshold value, indicating that an error condition exists with respect to the pair of computer systems; and if the error value is at least equal to a third threshold value, indicating that an error condition does not exist.