The " fourth chime " was a variation of the standard three-segment version , which repeated the closing " C " chime , to become " G-E-C-C " . It was initially adopted as a paging method for the New York City area , summoning employees listening at home to report for work at NBC headquarters in order to assist with an important developing story . However , as knowledge of the signal 's meaning spread , it also became a way to notify affiliate stations and knowledgeable listeners of pending urgent programming . The " fourth chime " was first used in 1937 in response to the Hindenburg disaster , and saw a majority of its use during World War Two . An NBC account of its employment at the start of the " D-day " invasion on June 6 , 1944 stated : " At '' 2:30 a.m. '' the network was put on ' flash ' basis ; the NBC four-chime-alert calling all newsmen and commentators to their microphones , key operating personnel to their stations , sounded from the newsroom control room . " There are very few recorded examples of fourth chime transmissions . Although NBC publicity , and some of the contemporary recordings , agree that the " fourth chime " sequence merely repeated a " C " at the end , some of the other recorded examples , although composed of 4 tones , have pitches that appear to be significantly different . The use of the " fourth chime " ended shortly after the close of World War Two
Hindenburg disaster
Hindenburg disaster
NBC chimes