Contrast control for a video amplifier including a spaced apart variable impedance device

Claim 1

IN A TELEVISION SIGNAL RECEIVING SET INCLUDING AN IMAGE DISPLAY DEVICE HAVING A VIDEO INPUT ELEMENT, A VIDEO AMPLIFIER STAGE COMPRISING: AN ELECTRONIC DISCHARGE DEVICE INCLUDING ANODE, CATHODE AND A PLURALITY OF CONTROL ELECTRODES; A SOURCE OF VIDEO SIGNAL CONNECTED WITH ONE OF SAID CONTROL ELECTRODES; A SOURCE OF ENERGIZING POTENTIAL INCLUDING A POINT OF REFERENCE POTENTIAL; AN IMPEDANCE CONNECTED BETWEEN SAID ANODE AND SAID SOURCE OF POTENTIAL ESTABLISHING AT SAID ANODE A POINT OF FIXED GAIN; A VARIABLE IMPEDANCE DEVICE REMOTELY LOCATED FROM SAID VIDEO AMPLIFIER INCLUDING TWO ENDS AND MOVABLE CONTACT; AND MEANS FOR CONNECTING SAID ELECTRONIC DISCHARGE DEVICE AND THE VIDEO INPUT ELEMENT OF SAID IMAGE DISPLAY DEVICE TO SAID VARIABLE IMPEDANCE DEVICE; INCLUDING FIRST, SECOND AND THIRD WIRES MAINTAINED IN FIXED SPACE RELATIONSHIP BY AN INSULATING MATERIAL AND HAVING SUBSTANTIALLY UNIFORM DISTRIBUTED CAPACITANCE THEREBETWEEN, SAID SECOND WIRE CONNECTING SAID ANODE TO ONE END OF SAID VARIABLE IMPEDANCE, SAID FIRST WIRE JOINING ANOTHER OF SAID CONTROL ELECTRODES OF SAID DEVICE WITH THE OTHER END OF SAID VARIABLE IMPEDANCE, AND SAID THIRD WIRE COUPLING SAID MOVABLE CONTACT TO THE INPUT ELEMENT OF SAID IMAGE DISPLAY DEVICE.