Automatic limit control apparatus

Claim 1

IN COMBINATION: A PROCESS CONTROLLER; A SOURCE OF ELECTRIC POWER TO THE PROCESS CONTROLLER; A FIRST SWITCHING MEANS FOR CONTROLLING THE FLOW OF ELECTRIC CURRENT TO THE PROCESS CONTROLLER; A SECOND SWITCHING MEANS FOR CONTROLLING THE FIRST SWITCHING MEANS; AND SWITCH MEANS RESPONSIVE TO A PREDETERMINED VALUE OF A PARAMETER IN SAID PROCESS IS OPERATING SAID SECOND SWITCHING MEANS, SAID SECOND SWITCHING MEANS INCLUDING A LATCHING RELAY WITH A SWITCH IN A CONDUCTING LINE LEADING TO THE FIRST SWITCHING MEANS, TRIPPING MEANS OPERATED BY THE SWITCH MEANS RESPONSIVE TO THE PREDETERMINED VALUE OF THE PARAMETER TO TRIP THE LATCHIN RELAY TO STOP THE FLOW OF CURRENT TO THE FIRST SWITCHING MEANS, SAID AN ELECTRIC CIRCUIT WITH AN ELECTRONIC TUBE HAVING AN ANODE, CONTROL GRID, AND A CATHODE SAID ELECTRONIC TUBE BEING BIASED TO A NONCONDUCTING STATE, AND THE SWITCH MEANS RESPONSIVE TO THE PREDETERMINED VALUE OF THE PARAMETER IS IN THE GRID-TO-CATHODE CIRCUIT OF THE ELECTRONIC TUBE AND RESPONSIVE TO THE PREDETERMINED VALUE TO REMOVE THE BIAS AND CAUSE THE ELECTRONIC TUBE TO CONDUCT TO OPERATE THE TRIPPING MEANS.