Chlorine concentration sensitive apparatus

Claim 1

IN A SYSTEM FOR DETECTING DEPARTURE OF THE CONTENT OF A CHEMICAL CHARACTERISTIC OF A LIQUID FROM A PREDETERMINED LIMITING VALUE, IN COMBINATION, A CONDUCTIVITY CELL COMPRISING ELECTRODE MEANS EXPOSED TO THE LIQUID AND HAVING TERMINALS FOR ELECTRICAL CONNECTION TO SAID CELL, SAID CELL BEING ADAPTED TO PROVIDE A CHANGE IN CONDUCTIVITY BETWEEN ITS TERMINALS UPON DEPARTURE OF SAID CHEMICAL CHARACTERISTIC OF THE LIQUID FROM SAID VALUE, A TRANSFORMER HAVING A SECONDARY IN SERIES WITH SAID TERMINALS AND A PRIMARY CONNECTED TO A SOURCE OF CURRENT SO THAT CURRENT IS SUPPLIED TO THE CELL FROM SAID SECONDARY, THE PRIMARY AND SECONDARY OF THE TRANSFORMER BEING ELECTRICALLY COUPLED SO THAT A CHANGE IN CURRENT FLOW IN THE SECONDARY RESULTING FROM A CHANGE IN CONDUCTIVITY IN THE CELL IS REFLECTED IN A CHANGE IN CURRENT FLOW IN THE PRIMARY, AN ELECTRONIC TUBE HAVING A CONTROL ELECTRODE, AND CIRCUIT MEANS CONNECTED FOR CONTROL BY SAID PRIMARY AND EXTENDING TO SAID CONTROL ELECTRODE FOR CONTROLLING SAID TUBE IN RESPONSE TO A PREDETERMINED CHANGE OF CURRENT FLOW THROUGH SAID PRIMARY, SAID ELECTRONIC TUBE HAVING AN ANODE AND AND ASSOCIATED ANODE CIRCUIT, SAID TUBE BEING ADAPTED TO PROVIDE CURRENT FLOW IN SAID ANODE CIRCUIT ONLY WHEN THERE IS AT LEAST A PREDETERMINED VOLTAGE ON THE CONTROL ELECTRODE, SAID FIRSTMENTIONED CIRCUIT MEANS COMPRISING AN IMPEDANCE CONNECTED IN SERIES WITH THE AFORESAID TRANSFORMER PRIMARY ACROSS SAID SOURCE OF CURRENT, SAID PRIMARY AND SAID IMPEDANCE CONSTITUTING A VOLTAGE DIVIDER AND SAID IMPEDANCE BEING CONNECTED TO SAID CONTROL ELECTRODE TO IMPRESS SAID PREDETERMINED VOLTAGE THEREON ONLY WHEN THE CONDUCTIVITY OF THE LIQUID EXCEEDS A PREDETERMINED VALUE, AND ALARM MEANS CONTROLLED BY SAID ANODE CIRCUIT AND BIASED TO OPERATE UNLESS CURRENT IS FLOWING IN SAID ANODE CIRCUIT.