Pin detection means

Claim 1

IN COMBINATION WITH A BOWLING ALLEY, APPARATUS FOR DETECTING THE PRESENCE OR ABSENCE OF A STANDING BOWLING PIN ON THE ALLEY BY DISTINGUISHING BETWEEN A FIRST CONDITION REPRESENTED BY A STANDING PIN AND SECOND CONDITION REPRESENTED BY A FALLEN PIN OR BY THE ABSENCE OF A PIN, COMPRISING, A FIRST MUTUAL INDUCTANCE DEVICE POSITIONED ADJACENT A PIN SPOT ON THE ALLEY, A SECOND MUTUAL INDUCTANCE DEVICE, AN ALTERNATING CURRENT SOURCE CONNECTED FOR ENERGIZING THE PRIMARIES OF BOTH DEVICES, SAID DEVICES BEING BALANCED TO PROVIDE EQUAL AND OPPOSITE OUTPUTS FROM THE SECONDARIES WHEN ONE OF SAID CONDITIONS EXISTS AND TO PROVIDE UNEQUAL OUTPUTS FROM THE SECONDARIES WHEN THE OTHER CONDITION EXISTS, AND A CIRCUIT CONNECTING THE SECONDARIES OF THE MUTUAL INDUCTANCES TO PROVIDE NO SIGNAL WHEN THE OUTPUTS FROM THE SECONDARIES ARE EQUAL AND A SIGNAL WHEN THE OUTPUTS FROM THE SECONDARIES ARE UNEQUAL.