Audimeter - Patented electronic device, (a.k.a. "the little black box") used by the A.C. Nielsen Company to monitor what television programs a viewing household is watching at any given moment. The Audimeter is placed into households nationwide to record TV viewing patterns. No household is a member for more than five years with 20% of the participants removed from the program each year. The Audimeter was originally invented by Louis Woodruff in 1930 to record what radio station any particular household was tuned into. The first television monitoring was done in September, 1950. As of September 1, 1987, the traditional Audimeter was replaced by a more complex unit called a "People Meter" which determined additional viewing factors such as sex and age.