The telephone was a crucial business technology even in the 1890s, when companies latched onto it as a way to speed up transactions, orders, and management. The weakness of the telephone was that, unlike the tradition written letter, there was no record of the content of a call after it was over. The desire for a telephone recorder for business purposes was one of the inspirations for Thomas Edison’s phonograph. Yet he discovered that the phonograph was not yet sensitive enough to do the job, and reworked it into a purely acoustic instrument by the time he announced it in late 1877.

The telegraphone, the first magnetic recorder, was specifically designed to record directly from the telephone lines. Its inventors imagined that it would be used as a telephone-based office dictation machine or telephone message system something like today’s voicemail. However, the American Telegraphone Company, which made the telegraphone under license in the U.S., and American Telegraphone’s distributor on the West Coast introduced the idea that sound recording could also be used for surveillance.

A 1906 article, probably written by an American Telegraphone official, describes the following fictitious scenario: Said Mr. Brown to Mr. Jones: “I never in my life agreed to do anything of the sort!” “and I say that you did!” Mr. Jones replied flatly. “And I say again that I did not!” Just here Mr. Brown brought his fist down with a slam that made things rattle on Mr. Jones’s desk. He faced him with a glare of defiance and perhaps a little cunning. “Then I must repeat that you did!” Mr. Jones pursued smoothly. “Last Thursday morning, when we discussed the affair over the telephone, you agreed to do precisely that and nothing else. My plans have been made accordingly, and the fact that you have changed your mind doesn’t alter matters a particle.” “Jones!” thundered Mr. Brown, “I defy you to prove–” “Hold on!” There was something odd about Mr. Jones’s voice. Mr. Brown started a little and stared more. From the queer machine on the desk across the room, the cover was removed, to reveal an instrument of most unusual appearance. Mr. Jones stepped to his own desk and extracted from a drawer a big spool of fine, shiny wire. He hurried back and slipped it into the machine; he pressed the button and the spool began to spin rapidly; he picked up a pair of telephone receivers and listened for a minute. After which, he smiled slightly and said: “If you’ll just come over here and listen for a minute–?. . .