The NBC logo really changed alot over the years. First it was a microphone surrounded by lighting bolts [1943]- which was a modification of a logo used by the radio network. The lighting bolts were also used on RCA's logo - which was a parent company. Then in 1954 it was a xylophone and mallet, along with the three tone 'bing-bong-bing.' And then, 1956, the peacock logos started - first it was really stylized [which was first used to identify nbc's color broadcasts]. The peacock was used to show the richness of color - and had 11 feathers. The logo became nbc's solo logo in 1986 because people identified with it so much.
In 1979 there was a new logo - with less colors and the bird facing forward, and not to the side. The bird's feet were gone and it became a simpler triangle shape. It was accompanied by the N to create a design called "The Perfect N"
The 6 feathered logo appeared in 1986 and had 6 primary colors - representing the network's divisions, which at the time was News, Sports, Entertainment, Stations, Network, and Productions. It was first introduced during NBC's 60th anniversary special. It was designed by Chermayeff & Geismar.