Before Cue Tones

One of the engineering trades had an interesting article on digital
splicing for local cable ad insertion. In the history section of the
article it says: "Since the beginning of local
advertising insertion, broadcasters indicated that an advertising avail
was coming by broadcasting a series of in-band dual-tone multifrequency (DTMF)
subcarrier audio cue tones."

Well if the author is just talking about cable insertion, well then he’s
correct. But the rag has the word "Broadcast" in its title, not cable,
so I’d like to wax poetic about the first system of local ad insertion –
GEC.

Yes, GEC – those three
chimes that were sounded at the end of every NBC network radio
program, telling the engineer at the local radio affiliate that his nap
was over and he had cue the local announcer to read those local ads!