The NBC Chimes Machine
By John Schneider
Play the NBC Chimes:
The sound of the NBC chimes is the sound of radio history itself. Probably no single sound better recalls the golden age of radio. The NBC chimes – the musical notes G-E-C – were played at the end of every NBC radio program beginning shortly after the network’s inception, and continued in daily use on NBC radio and television until 1971.
Shortly after the formation of the National Broadcasting Company in 1926, network executives became aware of confusion among the affiliate stations as to the exact when a program ended, and when it was safe to cut away for local announcements. The problem was assigned to a committee of three: Oscar Hanson, a former AT&T engineer; Ernest la Prade, an NBC orchestra leader; and Philip Carlin, an NBC announcer.
They decided that a musical signal of some kind would be an appropriate way to indicate the ending of all programs. At that time, it was common for radio stations to use the sounds of chimes, gongs, sirens and other mechanical devices as a signature sound for their station, so the choice of a chime by NBC was not unusual or particularly innovative. There is in fact some evidence that the chimes may have been inspired by a similar chime sequence used at that time by NBC affiliate WSB in Atlanta.
During 1927 and 1928, the committee experimented with several combinations of notes. A seven-note sequence which was first used, G-C-F-E-G-C-E, was determined to be too complicated for the announcers to play correctly on a consistent basis. It was first simplified to G-C-F-E, and finally to just G-E-C. This familiar sequence was heard for the first time on November 29, 1929.
The chimes were sounded at :29:30 and :59:30 of each hour, to indicate the start of the 30-second local station break. They were initially struck by hand by the announcer, using a set of hand-held chimes held up to the microphone. But there were inconsistencies in the way these chimes were played, in tempo, volume, and their exact timing.
It was finally determined that the best way to solve these problems was for the chimes to be generated mechanically.
The man who designed the chimes machine was Captain Richard H. Ranger, who was also the inventor of the electronic organ and the RCA facsimile. Ranger created a device resembling a music box, where fingers on a revolving drum plucked a set of reeds. There were three sets of eight reeds, one for each note, allowing the generation of the fundamental note plus several overtones.
Each reed formed one plate of a capacitor in an oscillator circuit, and the signal generated by all reeds was amplified by a single 6C6 pentode tube. It was activated by a timer, which would cut off the program two seconds before its end (whether it was finished or not!) and feed the chimes to the network.
NBC built a limited number of chime machines. NBC in San Francisco had two of them – the main and backup machines. Others were installed in other cities around the country where network programs were originated – Los Angeles, Chicago, New York, and perhaps a few others. It is likely that not more than a dozen chimes machines were ever made.
The photos on this page show one of the few chime machines still in existence, now in the hands of a private collector.
(NBC had the short-sighted habit of discarding large quantities of historical artifacts throughout its history. It’s only through the far-sightedness of a few NBC employees, who saved some of these items from the trash bins, that we can today experience many recorded programs, photos, and other memorabilia from that era.)
The unit shown is the chimes machine serial number 2, probably from the first group ever made. Its mechanical parts, although finely crafted, appear to have been hand made. This unit is no doubt the original chimes machine placed in operation at NBC’s studios at 111 Sutter Street in San Francisco.
The schematic diagram, also shown, indicates that serial number 5 was fabricated in 1933, so this machine would have predated it. The main cabinet contains the motor drive reed mechanism and amplifier, which is accessed by removing the front panel’s four thumbscrews.
The unit operated from an external power source, no doubt the same battery and motor-generator system that operated the audio amplifiers in the studios. The smaller box contains the timer and switches that operate the chimes for both studio and “NEMO” broadcast lines. (“NEMO” was a term used in early radio to indicate a remote broadcast. It comes from a telephone term, and stands for “Not Emanating Main Office.”)
The chime machine could be operated in an automatic mode by the clock, which was the usual method of operation, or manually by the announcer in the event of programs with imprecise ending times, such as sports broadcasts.
The NBC chimes were officially registered with the U.S. Patent Office in 1950 as a registered service mark, the first known case of a sound receiving trademark protection.
The NBC chimes were last heard regularly on NBC television in 1976, used to mark the 50th anniversary of the network.
A History of the NBC Chimes, by Bill Harris
More on the NBC Chimes, by Brian Wickham
A Backstage Visit to Radio City, by Fred Krock
Author's inspection of a chimes machine in the hands of a private collector
Copyright © 1999 John F. Schneider. All rights reserved.