Alternator failure warning indicator

Claim 1

In an aircraft equipped with an electrical system comprising an alternator with solid state diode rectifiers producing direct current as the principal component of the total current output when operating normally, the improvement comprising a warning indicator selected from the group consisting of those giving visible and audible signals, said indicator giving a tangible warning to an aircrew member of said aircraft when the alternating current component of said total current reaches a predetermined level symptomatic of incipient failure of some component of said alternator or said solid state rectifiers, said indicator comprising means conducting current from said electrical system to switching means responsive to a preselected level of the alternating current from said electrical system comprising, in the positive side of said switching means, an integrated circuit which will accept an input ranging from 12 to 24 nominal volts and have an output of 12 nominal volts, in the negative side a blocking capacitator, a diode rectifier and a variable resistance controlling the voltage to the base of an NPN transistor, the collector of said transistor directly connected to the base of a second NPN transistor such that when said first transistor is conducting said second transistor is non conducting and vice versa such that when said first transistor is non-conducting said second transistor is conducting current in series with said warning indicator and activating said indicator, the level of said alternating current which will activate said indicator being controlled by a pre-selected level of said variable resistance.