Electrical power system with fault tolerant control unit

An electrical power system comprising:

• a plurality of generators;
• a plurality of contactors individually connected in series with the output of said generators and a plurality of power buses;
• computer means having input means for receiving information signals and output means for delivering digitally encoded information signals;
• said computer means being adapted to treat said received information signals in accordance with a predetermined program and to produce said digitally encoded output information signals;
• said computer means being further adapted to run through a self-test program and to generate a digital control word at the end of each test program sequence after a fixed time interval following the initiation of said self-test program, wherein said control word encodes the test program results;
• a memory for storing predetermined digitally encoded messages and self-test routine instructions in a given sequence and outputting said messages and said self-test routine instructions;
• a comparator for comparing said predetermined digitally encoded messages from said memory means and said digitally encoded control words from said computer means, producing an output signal at a first logic level when said messages are equivalent to said control words and producing an output signal at a second logic level when said messages are not equivalent to said control words;
• means for initializing said memory such that a selected predetermined digitally encoded message appears at the output of said memory when electrical power is applied to the control unit;
• feedback means responsive to a transition in said comparator means output signal which delivers signals to said memory means for the purpose of indexing said predetermined digitally encoded messages and self-test routine instructions after said fixed time interval following the occurrence of said transition;
• and
• output means responsive to said comparator means for controlling said contactors in accordance with said computer means output information signals when the comparator means output signal periodically switches between said first and second logic levels to define a square wave, and for driving said contactors into a predetermined state when the comparator means output signal fails to define a square wave.