Valve and control circuit therefor

Claim 1

A FLUID PRESSUE CONTROL SYSTEM FOR CONTROLLING PRESSURE IN A GENERALLY CHANGING MANNER, SAID SYSTEM COMPRISING A VALVE ADAPTED TO BE OPERATED BY MAGNETOMOTIVE AND FLUID PRESSURE FORCES, SAID VALVE INCLUDING A CONTROL PORT, AN ELEMENT ALIGNED WITH SAID PORT AND URGED AWAY FROM IT BY FLUID PRESSURE AT SAID PORT AND URGED IN THE OPPOSITE DIRECTION BY SAID MAGNETOMOTIVE FORCES; AN ELECTRIC TRANSDUCER FOR PROVIDING SAID MAGNETOMOTIVE FORCES; AND AN ELECTRIC CIRCUIT INCLUDING AUTOMATICALLY OPERABLE MEANS FOR SUPPLYING AN ELECTRICAL INPUT TO SAID TRANSDUCER WHICH CHANGES GRADUALLY OVER A PERIOD OF TIME, SAID CIRCUIT COMPRISING FIRST AND SECOND LEADS FOR CONNECTION RESPECTIVELY TO THE NEGATIVE AND POSITIVE TERMINALS OF A SOURCE OF CONSTANT POTENTIAL, A VACUUM TUBE INCLUDING A GRID, A CATHODE AND A PLATE, MEANS CONNECTING SAID TRANSDUCER TO SAID SECOND LEAD, RESISTIVE MEANS EFFECTIVE TO BIAS SAID CATHODE POSITIVE WITH RESPECT TO SAID FIRST LEAD, A FIRST VARIABLE RESISTOR AND CAPACITOR CONNECTED IN PARALLEL BETWEEN SAID GRID AND A JUNCTION, A SECOND VARIABLE RESISTOR AND CAPACITOR CONNECTED IN PARALLEL FROM SAID JUNCTION TO SAID FIRST LEAD, MEANS INCLUDING A SWITCH DISCONNECTABLY CONNECTING SAID FIRST LEAD TO SAID GRID, AND MEANS INCLUDING A SWITCH AND A RESISTOR DISCONNECTABLY CONNECTING SAID JUNCTION TO SAID FIRST LEAD.