Warning system for indicating failure of electrical circuits

Claim 1

An electrical circuit comprising a source of electrical energy, first and second power utilization means for respectively receiving current from said source, warning means responsive to electrical energy, normally open switching means for connecting said warning means to said source of electrical energy, said switching means being responsive to a magnetic field, and means forming first and second current paths for respectively transmitting said current to said first and second power utilization means, portions of said paths being disposed such as to create substantially equal magnetic fields substantially cancelling each other, said switching means being closed when said magnetic fields become unequal by a predetermined amount for turning on said warning means, wherein said current path portions form separate windings defining a coil surrounding said switching means, said coil being so formed that electrical current passes through each of said windings in opposite directions to provide substantially equal and opposite magnetic fields and wherein each of said windings is an electrical wire of a predetermined gauge, said coil being formed by alternate turns of said windings about a common axis such that each turn of one of said windings is adjacent to each turn of the second of said windings, each of said windings being connected in each of said current paths such that current normally flows in said paths in opposite directions, and wherein said switching means comprises a pair of movable contacts, one of which is connected to said electrical source and the other is connected to said warning means, said movable contacts being normally open and adapted to engage one another to close said switch in response to exposure to a magnetic field of a predetermined intensity.