Permissible Exposure Limit
i think it was in the year 1924, but i am not sure it was actuly 1922
the year 1956
pel , an abbreviation for pixel. Also sometimes used to refer to a subpixel. Permissible Exposure Limit , a legal limit defined by the Occupational Safety and Health Administration in the United...
The term 'pel' means (computer science) the smallest discrete component of an image or picture on a CRT screen (usually a colored dot)