Self checking digital computer system

Claim 1

A REMAINDER MODULO-N CHECKING SYSTEM COMPRISING SOURCES OF FIRST AND SECOND BINARY SIGNALS REPRESENTATIVE OF RESPECTIVE FIRST AND SECOND DECIMAL NUMBERS, FIRST AND SECOND MEANS COUPLED RESPECTIVELY TO SAID FIRST AND SECOND SOURCES FOR PRODUCING BINARY SIGNALS REPRESENTATIVE OF THE SUM (MODULO-N) OF THE DIGITS OF SAID RESPECTIVE FIRST AND SECOND DECIMAL NUMBERS, THIRD MEANS COUPLED TO SAID FIRST AND SECOND MEANS FOR MARKING ONE OF 2N-1 OUTPUT LINES IN ACCORDANCE WITH THE COMBINED OUTPUT CONDITIONS OF SAID FIRST AND SECOND MEANS, ABSENT THAT COMBINATION ASSOCIATED WITH SIMULTANEOUS VALUES OF ZERO (MODULO-N), AND A PLURALITY OF SWITCHING CIRCUITS COUPLED TO SAID THIRD MEANS FOR OPERATING ON THE MARKING SIGNAL PRODUCED AT THE OUTPUT THEREOF IN ACCORDANCE WITH A SELECTED ONE OF THREE ARITHMETIC OPERATIONS.