This is the NBC section of
The Broadcast Archive
Barry Mishkind - The Eclectic Engineer
The story about the NBC chimes.
Like many aspects of broadcast history, the actual story of
how the NBC chimes originated has several variations.
One answer for the origin of the tones G-E-C is found at the Pavek
Broadcast Museum in Minneapolis. (BTW, this is a fine museum, with a lot of old
radios, an old transmitter, "ham shack", early TV items, and even a
working spark gap transmitter from 1912!)
Next to one of the original NBC Chime boxes, made by the J.C.Deagan Company in
Chicago until 1954, is a history card explaining that after the NBC network
began, a coordinating signal was needed so the stations would know when programs
ended. Oscar Hanson, Earnest LaPrade and Phillips Carlin were assigned the task
of designing a "signature".
From 1927 to 1928 they experimented with various sequences of as many as seven
tones, ie: G-C-G-E-G-C-E. However, since the air men found it difficult to
repeatedly do this accurately, it was reduced to four, G-G-G-E, and then on
11/29/29, the G-E-C triad was first broadcast.
Starting in 1932, the tones were generated by an "electronic music
box", each note being composed of eight partial notes in the form of metal
reeds. The 24 reeds were "plucked" by a mechanical finger.
"Technically, each set of parallel metal reeds formed a small condenser,
the capacitance of which was varied by the vibration of the reeds." The
notes were amplified and sent out over the network.
During World War II, a fourth chime (actually a second "C") was used
to alert the NBC News department of War Bulletins. The first instance was the
crash of the Hindenberg.
The three tone sequence was trademarked (the first audible trademark) in 1950.
(The above material was summarized from an abstract noted (c) 1976 Rod Phillips)
A similar, but more detailed explanation comes from Bill Harris, who
maintains an article on his web
site, including some audio cuts of the NBC chimes. As mentioned in Bill's
research, several stations, including WSB, Atlanta; KFI, Los Angeles; and WGY,
Schenectady claim independently to have originated the tones, aside from the NBC
network. Bill also addresses the matter of the "fourth chime."
Interestingly, in the late 1930s, NBC sold a small, three note, chime as a
promotional item. Apparently, it is not very rare.