A variant sequence with an additional note, G-E'-C'-G, known as "the fourth chime", was used during significant events of extreme urgency (including during World War II, especially in the wake of the December 1941 attack on Pearl Harbor; on D-Day and during disasters). The NBC chimes were mechanized in 1932 by Rangertone founder Richard H. Ranger; their purpose was to send a low-level signal of constant amplitude that would be heard by the various switching stations manned by NBC and AT&T engineers, and to be used as a system cue for switching individual stations between the Red and Blue network feeds. Contrary to popular legend, the G-E'-C' notes were not originally intended to reference to the General Electric Company (an early shareholder in NBC's founding parent RCA and whose Schenectady, New York radio station, WGY, was an early affiliate of NBC Red). The three-note sequence remains in use by the NBC television network, most notably incorporated into the John Williams-composed theme music used by NBC News, "The Mission" (first composed in 1985 for NBC Nightly News).
NBC has thirteen owned-and-operated stations and nearly 200 affiliates throughout the United States and its territories, some of which are also available in Canada via pay-television providers or in border areas over-the-air; NBC also maintains brand licensing agreements for international channels in South Korea and Germany . 
They have an ancient legacy but every Olympics features new athletes and events that keep the Games current and fresh. Here's a look at what will be new at the PyeongChang Winter Olympics.