Lamp outage indicator circuit
First Claim
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1. A lamp outage indicator for an incandescent lighting system having a source of direct current, a first resistance of relatively small value and a first incandescent lamp connected in series across said source, which comprises:
- a voltage divider network comprising a second resistance and a third resistance connected across said source of direct current;
a first two terminal voltage sensitive indicator device and a fourth resistance connected in series, with the free terminal of the said first voltage sensitive indicator connected intermediate said second and third resistances, and the free terminal of the said fourth resistance connected in common with the incandescent lamp and the source of direct current; and
a second two terminal voltage sensitive indicator device, the first terminal of said device being connected intermediate said first two terminal voltage indicating device and said fourth resistance, the second terminal of said device being connected intermediate said first resistance and said incandescent lamp.
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Abstract
An indicator circuit for indicating whether an incandescent type lamp is burned out. The indicator circuits include a voltage reference source and an indicator LED which is normally biased just below the knee of its conduction curve, but which is biased into conduction whenever the monitored lamp burns out. A bridge circuit is utilized so that relatively small variations in power source voltage do not affect the operating point of the circuit.
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Citations
4 Claims
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1. A lamp outage indicator for an incandescent lighting system having a source of direct current, a first resistance of relatively small value and a first incandescent lamp connected in series across said source, which comprises:
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a voltage divider network comprising a second resistance and a third resistance connected across said source of direct current; a first two terminal voltage sensitive indicator device and a fourth resistance connected in series, with the free terminal of the said first voltage sensitive indicator connected intermediate said second and third resistances, and the free terminal of the said fourth resistance connected in common with the incandescent lamp and the source of direct current; and a second two terminal voltage sensitive indicator device, the first terminal of said device being connected intermediate said first two terminal voltage indicating device and said fourth resistance, the second terminal of said device being connected intermediate said first resistance and said incandescent lamp. - View Dependent Claims (2, 3, 4)
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Specification