Patent ID: 8309889
Filing Date: 2012-11-13
Classification: H05B

Abstract:
1. In combination, two supply voltage lines; a pair of electric heaters electrically connected in series across said voltage lines and having a tap therebetween; an indicating lamp having a first lead electrically connected to said tap for indicating a failure of one of said pair of electric heaters; and an electrical circuit including a pair of resistors connected to a second lead of said lamp; and a pair of diodes, each said diode being electrically connected in series with a respective one of said resistors to form a resistor-diode pair, each said resistor-diode pair being electrically connected said second lead of said lamp and said voltage line whereby during operation of said electric heaters voltage to said lamp is maintained below a predetermined starting level and in response to failure of a respective one of said heaters, voltage passes through one of said diodes, said respective resistor, said lamp and the other of said heaters to effect illumination of said lamp.