Tracing device utilizing line-scanning photoelectric pick-up means

Claim 1

AN AMPLIFIER FOR USE WITH APPARATUS WHICH OPERATES RESPONSIVE TO REPEATED POTENTIAL VARIATIONS HAVING GENERALLY PREDETERMINED PERIODS AS DISTINCT FROM SPURIOUS POTENTIAL VARIATION, THE OPERATION OF SAID APPARATUS TO BE STOPPED ON THE DISAPPEARANCE OF SAID REPEATED POTENTIAL VARIATIONS, THE SAID AMPLIFIER COMPRISING AN INPUT VALVE HAVING A CONTROL ELECTRODE AND PRINCIPAL ELECTRODES, MEANS CONNECTED TO SAID PRINCIPAL ELECTRODES FOR IMPRESSING A SUBSTANTIALLY NON-VARYING ENERGIZING POTENTIAL BETWEEN SAID PRINCIPAL ELECTRODES, MEANS CONNECTED TO SAID CONTROL ELECTRODE AND ONE OF SAID PRINCIPAL ELECTRODES FOR IMPRESSING BOTH SAID REPEATED VARIATIONS AND SAID SPURIOUS VARIATION BETWEEN SAID CONTROL ELECTRODE AND SAID PRINCIPAL ELECTRODE, SAID REPEATED VARIATIONS AND SAID SPURIOUS VARIATIONS BEING IMPRESSED TOGETHER WHEN SAID REPEATED VARIATIONS ARE PRESENT AND SAID SPURIOUS VARIATIONS BEING IMPRESSED ALONE WHEN SAID REPEATED VARIATIONS ARE NOT PRESENT, A TIME CONSTANT NETWORK HAVING A TIME CONSTANT SUBSTANTIALLY LONGER THAN THE LONGEST OF SAID PERIODS OF SAID REPEATED VARIATION, MEANS CONNECTED TO SAID PRINCIPAL ELECTRODES IN CURRENT TRANSMITTING RELATIONSHIP TO SAID NETWORK, SAID CONNECTING MEANS INCLUDING MEANS FOR SUPPRESSING ANY DIRECT CURRENT COMPONENT OF THE POTENTAL APPEARING ACROSS SAID PRINCIPAL ELECTRODES AND ALSO INCLUDING MEANS IMPEDING THE FLOW OF CURRENT FROM SAID PRINCIPAL ELECTRODES TO SAID NETWORK SO THAT POTENTIAL OF A SUBSTANTIAL MAGNITUDE DEPENDENT ON THE AMPLITUDE OF SAID REPEATED VARIATION IS BUILT UP ON SAID NETWORK WHEN SAID REPEATED VARIATIONS ARE APPRECIABLY PRESENT AND THE POTENTIAL ON SAID NETWORK REMAINS LOW IN THE ABSENCE OF SAID REPEATED VARIATIONS, AN OUTPUT VALVE HAVING A CONTROL ELECTRODE AND PRINCIPAL ELECTRODES MEANS CONNECTED TO SAID PRINCIPAL ELECTRODES OF SAID OUTPUT VALVE FOR IMPRESSING BETWEEN SAID PRINCIPAL ELECTRODES A NONVARYING ENERGIZING POTENTIAL, AND MEANS CONNECTING SAID NETWORK BETWEEN SAID CONTROL ELECTRODE AND ONE OF SAID PRINCIPAL ELECTRODES OF SAID OUTPUT VALVE TO IMPRESS THE POTENTIAL ON SAID NETWORK IN CONTROLLING RELATIONSHIP BETWEEN SAID LAST-NAMED CONTROL ELECTRODES AND PRINCIPAL ELECTRODES TO CONTROL THE CONDUCTION OF SAID OUTPUT VALVE.