class P ballast
Also found in: Dictionary, Thesaurus, Medical, Financial, Wikipedia.
1. Coarse stone, gravel, slag, etc., used as an underlayer for poured concrete.
2. A device used to provide the required starting voltage and operating current for fluorescent, mercury, or other electric-discharge lamps.
3. Class P: A ballast for a fluorescent lamp which meets the requirements of the Underwriters’ Laboratories, Inc.; includes an automatic resetting thermal protector to remove the ballast from the circuit if its temperature exceeds a specified value.
4. Same as constant-wattage ballast.