Electron beam intensity control circuit

Claim 1

IN AN ELECTRON BEAM DEVICE IN WHICH A BEAM IS DEFLECTED IN A PRE-ESTABLISHED PATTERN OVER A GIVEN AREA, MEANS FOR BLANKING SAID BEAM BOTH DURING RETRACE SWEEPS OF SAID BEAM AND WHEN THE SPEED OF SAID DEFLECTION FALLS BELOW A PREDETERMINED VALUE COMPRISING ENERGIZING MEANS FOR DEVELOPING SAID BEAM, MEANS RESPONSIVE TO AN ENERGIZING CURRENT FOR DEFLECTING SAID BEAM, MEANS FOR SAMPLING SAID ENERGIZING CURRENT AND PRODUCING A CONTROL VOLTAGE PROPORTIONAL TO THE RATE OF CHANGE OF SAID ENERGIZING CURRENT, MEANS RESPONSIVE TO SAID CONTROL VOLTAGE FOR PRODUCING A PRE-ESTABLISHED POTENTIAL WHEN SAID CONTROL VOLTAGE IS OF A PREDETERMINED POLARITY WITH RESPECT TO THE REFERENCE POTENTIAL SAID LAST-MENTIONED MEANS COMPRISING A DIRECT-CURRENT AMPLIFIER HAVING AN INPUT DIRECTLY COUPLED TO SAID MEANS FOR SAMPLING SAID ENERGIZING CURRENT, SAID AMPLIFIER BEING BIASED TO PROVIDE A POTENTIAL AT ITS OUTPUT WHICH IS MAINTAINED AT A PREDETERMINED VALUE WHEN THE POTENTIAL APPLIED TO SAID INPUT IS OF SAID PREDETERMINED POLARITY WITH WITH RESPECT TO SAID REFERENCE POTENTIAL.