Continuity field test bridge circuit with diode-controlled visual indicator means

Claim 1

A TEST BRIDGE CIRCUIT FOR CHECKING ELECTRICAL APPARATUS FOR NORMAL AND ABNORMAL OPEN-CIRCUIT AND CLOSED CIRCUIT CONDITIONS, COMPRISING IN COMBINATION, AN ELECTRICAL BRIDGE CIRCUIT HAVING OPPOSITE POSITIVE AND NEGATIVE INPUT SUPPLY TERMINALS AND FOUR BALANCED RESISTANCE ARMS CONNECTED BETWEEN SAID INPUT TERMINALS IN TWO PARALLEL BRANCH CIRCUITS WITH AN INTERMEDIATE BRIDGE OUTPUT TERMINAL CONNECTED THEREBETWEEN IN EACH BRANCH AND EFFECTIVELY AT OPPOSITE DIAGONALS WITH RESPECT TO THE POSITIVE AND NEGATIVE INPUT TERMINALS, A DIODE ELEMENT CONNECTED IN AN ARM OF ONE OF SAID BRANCH CIRCUITS ADJACENT TO AND DIRECTLY WITH THE POSITIVE INPUT SUPPLY TERMINAL AND POLED IN A DIRECTION TO PREVENT CURRENT FLOW FROM SAID TERMINAL IN SAID ARM AND BRANCH, A CURRENT-RESPONSIVE VISUAL INDICATOR DEVICE CONNECTED SERIALLY IN SAID ARM BETWEEN SAID DIODE ELEMENT AND THE INTERMEDIATE BRIDGE OUTPUT TERMINAL OF THE BRANCH, MEANS PROVIDING OPEN-CIRCUIT AND CLOSED-CIRCUIT TEST CONNECTIONS RESPECTIVELY WITH SAID INTERMEDIATE OUTPUT TERMINAL AND WITH SAID RESISTANCE ARM BETWEEN THE RESISTANCE PORTION THEREIN AND SAID DIODE ELEMENT, SAID TEST CONNECTIONS HAVING A COMMON TEST CIRCUIT RETURN CONNECTION WITH THE POSITIVE TERMINAL OF SAID BRIDGE CIRCUIT, A