were played by hand by the announcers, which led to occasional errors and undesirable variations. In 1932 a standardized "chimeless chime", which promised to play the notes consistently — one reviewer commented that "there will be no more sour notes from those NBC chimes — was developed by Richard H. Ranger, a former RCA engineer who had invented an electronic organ. Ranger's creation was a music box-style electro-mechanical device, which played the three-note sequence at the push of a button. The initial installation was made at New York City headquarters, and went into operation on September 18, 1932. Following successful tests, the network ordered multiple additional units, which were distributed to major sites throughout the United States, including Los Angeles, New York City, Chicago and San Francisco (which had two machines, a main one and a backup). About a dozen of the Ranger units are estimated to have been constructed, a few of which survive in collections. Around 1941 the Rangertone devices started to be replaced with an all-electronic system developed by NBC engineers. By the mid-1980s, these dedicated devices had been replaced by a magnetic tape cartridge recording of a chimes machine that was played back as needed. The "fourth chime" 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 II. 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,