Duplexing system for controlling online and standby conditions of two computers

Claim 1

THE COMBINATION OF TWO COMPUTERS EACH INCLUDING VALIDATION PULSE GENERATING MEANS UNDER PROGRAM CONTROL FOR GENERATING PROGRAM VALIDATION PULSES INDICATIVE OF NORMAL ON-LINE, STANDBY AND FAILED CONDITIONS IN THE RESPECTIVE COMPUTER, PROGRAM INTERRUPT MEANS, COMMAND AND STATUS MEANS FOR CONTROLLING THE OPERATION OF THE COMPUTER AFTER ITS PREVIOUS PROGRAM IS INTERRUPTED, AND INPUTOUTPUT SWITCHES FOR CONNECTING COMMON INPUT-OUTPUT DEVICES WITH THE RESPECTIVE COMPUTER, A DUPLEXING CONTROL UNIT INCLUDING MEANS CONNECTED TO RECEIVE SAID PROGRAM VALIDATION PULSES FROM BOTH COMPUTERS AND OPERATIVE TO GENERATE A "STANDBY" SIGNAL LEVEL ON THE REPEATED OCCURRENCE WITH AT LEAST A PREDETERMINED FREQUENCY OF SAID STANDBY PULSES AND THE ABSENCE OF SAID FAILED PULSE FROM A STANDBY ONE OF SAID COMPUTERS, AND TO GENERATE AN "ON-LINE" SIGNAL LEVEL ON THE REPEATED OCCURRENCE WITH AT LEAST A PREDETERMINED FREQUENCY OF SAID NORMAL PULSES AND THE ABSENCE OF SAID FAILED PULSE FROM THE OTHER ON-LINE ONE OF SAID COMPUTERS, AND MEANS RESPONSIVE TO THE TERMINATION OF SAID "ON-LINE" SIGNAL LEVEL TO APPLY SIGNALS TO THE PROGRAM INTERRUPT MEANS, THE COMMAND AND STATUS MEANS AND THE INPUT-OUTPUT SWITCHES OF BOTH COMPUTERS, WHEREBY AUTOMATICALLY TO CAUSE THE STANDBY ONE OF THE COMPUTERS TO REPLACE THE OTHER COMPUTER IN THE ON-LINE CONDITION, AND ERROR DETECTION MEANS RESPONSIVE TO INCONSISTENT CONDITIONS IN SAID DUPLEXING CONTROL UNIT AND OPERATIVE TO APPLY A SIGNAL TO SAID COMMAND AND STATUS MEANS IN BOTH COMPUTERS TO CAUSE THE COMPUTERS TO IGNORE ALL OTHER SIGNALS FROM SAID DUPLEX CONTROL UNIT.