Multi-point null-balance bridge system

Claim 1

IN A DEVICE FOR MONITORING AT A REMOTE STATION A PLURALITY OF VARIABLE CONDITIONS INDICATED AS VARYING IMPEDANCES, THE COMBINATION COMPRISING; AN A.C. ENERGIZED IMPEDANCE BRIDGE STRUCTURE INCLUDING FIRST AND SECOND IMPEDANCE ARMS EACH OF SWITCHINGLY SELECTABLE VALUE TO ESTABLISH AT BRIDGE BALANCE AN IMPEDANCE RATIO, SAID ARMS BEING PARALLEL CONNECTED FOR SERIES ENERGIZATION WITH THIRD AND FOURTH ARMS, RESPECTIVELY, SAID THIRD ARM SWITCHINGLY INCLUDING ONE OF A PLURALITY OF IMPEDANCES EACH VARIED BY A SAID CONDITION, SAID FOURTH ARM BEING A SINGLE IMPEDANCE ADJUSTABLY VARIABLE TO BALANCE SAID BRIDGE ACCORDING TO SAID RATIO DETERMINED BY SAID FIRST AND SECOND ARMS; SWITCH MEANS REMOTELY OPERABLE TO SELECT IN SUCCESSION CORRESPONDING SAID IMPEDANCE VALUES IN SAID FIRST, SECOND AND THIRD ARMS, MEANS FOR ADJUSTING SAID FIRST AND SECOND ARM IMPEDANCE VALUES WHEREBY A SINGLE ADJUSTMENT OF SAID FOURTH ARM REPRESENTS A BRIDGE BALANCE FOR EACH OF SAID PLURALITY OF IMPEDANCES AT A PREDETERMINED NORMAL VALUE; MEANS INCLUDING A MOTOR OPERATIVELY LINKED TO VARY SAID FOURTH ARM IMPEDANCE IN RESPONSE TO UNBALANCE OF SAID BRIDGE AND ENERGIZED TO REBALANCE THE BRIDGE; REPEATING MOTOR MEANS AT SAID STATION INDICATING THE EXTENT OF OPERATION OF FIRST SAID MOTOR TO EFFECT SAID REBALANCING; AND MEANS AT SAID STATION FOR REMOTELY SELECTING ANY OF SAID PLURALITY OF IMPEDANCES INDICATIVE OF CONDITIONS, INCLUDING INDICATING MEANS TO SHOW WHICH THEREOF IS SELECTED, AUTOMATIC CORRECTING MEANS TO CONTINUE SELECTING UNTIL SAID SELECTED IMPEDANCE IS IN CIRCUIT, AND MEANS TO INDICATE WHEN A SAID SELECTED IMPEDANCE IS NOT IN CIRCUIT.