Patent ID: 7659671

Claim:
A controller for a fluorescent light fixture having first, second, third and fourth fluorescent bulbs, the controller comprising: a first light sensor that detects light from the first fluorescent bulb and outputs a first logic state when an amount of detected light from the first fluorescent bulb is above a predetermined threshold and outputs a second logic state when the amount of detected light from the first fluorescent bulb is below the predetermined threshold; a second light sensor that detects light from the second fluorescent bulb and outputs the first logic state when an amount of detected light from the second fluorescent bulb is above the predetermined threshold and outputs the second logic state when the amount of detected light from the second fluorescent bulb is below the predetermined threshold; a first switch mechanism that controls when the first and second fluorescent bulbs are illuminated by applying power simultaneously to the first and second fluorescent bulbs; a second switch mechanism that controls when the third and fourth fluorescent bulbs are illuminated by applying power simultaneously to the third and fourth fluorescent bulbs; a visible warning light that is activated to indicate when one of the first and second fluorescent bulbs has failed; and a controller mechanism that activates the first switch mechanism to apply power simultaneously to the first and second fluorescent bulbs until the first light sensor outputs the second logic state to indicate the first fluorescent bulb has failed when the second light sensor outputs the first logic state to indicate the second fluorescent bulb has not failed, and in response to the second logic state from the first light sensor, the controller mechanism deactivates the first switch mechanism to remove power simultaneously from the first and second fluorescent bulbs, activates the second switch mechanism to apply power simultaneously to the third and fourth fluorescent bulbs, and activates the visible warning light.