Discriminating safety monitor for servo systems

Claim 1

IN A DISCRIMINATING SAFETY MONITOR FOR A DUAL SIGNAL CHANNEL SERVO SYSTEM, (1) MEANS FOR GENERATING AN ERROR SIGNAL HAVING AN AMPLITUDE AND PHASE REPRESENTATIVE OF THE MAGNITUDE AND SENSE OF THE SYSTEM ERROR, (2) FIRST AND SECOND DUAL ERROR SIGNAL CHANNELS, SAID FIRST ERROR SIGNAL CHANNEL HAVING A FIRST IN-PHASE NORMAL CHANNEL AND A FIRST OUT-OF-PHASE STANDBY CHANNEL, SAID SECOND ERROR SIGNAL CHANNEL HAVING A SECOND OUT-OF-PHASE NORMAL CHANNEL AND A SECOND IN-PHASE STANDBY CHANNEL, (3) FIRST BIASING MEANS CONNECTED TO SAID FIRST AND SECOND NORMAL CHANNELS FOR BIASING SAID CHANNELS TO PASS ERROR SIGNALS ABOVE A FIRST PREDETERMINED AMPLITUDE OVER A NORMAL RANGE, (4) SECOND BIASING MEANS CONNECTED TO SAID FIRST AND SECOND STANDBY CHANNELS TO BIAS SAID STANDBY CHANNELS TO PASS ERROR SIGNALS ABOVE A SECOND PREDETERMINED AMPLITUDE HIGHER THAN SAID FIRST PREDETERMINED AMPLITUDE AND ABOVE SAID NORMAL RANGE, (5) FIRST SIGNAL SUMMING MEANS CONNECTED TO SAID FIRST IN-PHASE NORMAL CHANNEL AND TO SAID SECOND IN-PHASE STANDBY CHANNEL FOR PROVIDING A FIRST OUTPUT SIGNAL IN ACCORDANCE WITH ERROR SIGNALS FROM SAID FIRST NORMAL CHANNEL OVER SAID FIRST NORMAL RANGE AND FROM SAID SECOND STANDBY CHANNEL ABOVE SAID FIRST PREDETERMINED AMPLITUDE TO PROVIDE STANDBY OPERATION, (6) SECOND SIGNAL SUMMING MEANS CONNECTED TO SAID SECOND OUT-OF-PHASE NORMAL CHANNEL AND SAID FIRST IN-PHASE STANDBY CHANNEL FOR PROVIDING A SECOND OUTPUT SIGNAL IN ACCORDANCE WITH ERROR SIGNALS FROM SAID SECOND NORMAL CHANNEL OVER SAID FIRST NORMAL RANGE AND FROM SAID FIRST STANDBY CHANNEL ABOVE SAID FIRST PREDETERMINED AMPLITUDE TO PROVIDE STANDBY OPERATION, (7) AND SERVO MEANS RESPONSIVE TO SAID FIRST AND SECOND OUTPUT SIGNALS.