Printer light intensity control circuit

Claim 1

IN A SYSTEM FOR CONTROLLING THE CURRENT APPLIED FROM AN ALTERNATING-CURRENT SOURCE TO A LOAD WITH A MAGNETIC AMPLIFIER WHICH IS RESPONSIVE TO A CONTROL CURRENT APPLIED TO ITS CONTROL WINDING, THE IMPROVEMENT FOR LINEARIZING THE RELATIONSHIP OF THE CONTROL CURRENT TO THE ROOT MEAN SQUARE VALUE OF THE OUTPUT VOLTAGE WHICH IS APPLIED TO THE SAID LOAD COMPRISING A FEEDBACK WINDING ON SAID MAGNETIC AMPLIFIER, AND FEEDBACK-NETWORK MEANS CONNECTED BETWEEN SAID LOAD AND SAID FEEDBACK WINDING, SAID FEEDBACK NETWORK MEANS INCLUDING A FILTER FOR RECTIFYING THE VOLTAGE APPLIED THERETO, AND A VARIABLE RESISTANCE MEANS HAVING THE CHARACTERISTICS SUCH THAT ITS RESISTANCE VARIES SUBSTANTIALLY INVERSELY WITH THE FOURTH POWER TO THE VOLTAGE APPLIED ACROSS IT, AND MEANS FOR CONNECTING SAID VARIABLE RESISTANCE MEANS ACROSS THE OUTPUT OF SAID FILTER, SAID FEEDBACK NETWORK MEANS ESTABLISHING A LINEAR RELATIONSHIP BETWEEN THE CONTROL CURRENT APPLIED TO SAID CONTROL WINDING AND THE ROOT MEANS SQUARE VOLTAGE EXISTING ACROSS SAID LOAD IN RESPONSE TO THE OUTPUT OF SAID MAGNETIC AMPLIFIER.