Eavesdropping technologies of various sorts have been around for centuries. Prior to the invention of recorded sound, the vast majority of listening devices were extensions of the built environment. Perhaps nodding to the origins of the practice (listening under the eaves of someone else’s home, where rain drops from the roof to the ground), early modern architects designed buildings with structural features that amplified private speech. The Jesuit polymath Athanasius Kircher devised cone-shaped ventilation ducts for palaces and courts that allowed the curious to overhear conversations. Catherine de’ Medici is said to have installed similar structures in the Louvre to keep tabs on individuals who might have plotted against her. Architectural listening systems weren’t always a product of intentional design. Domes in St. Paul’s Cathedral in London and the US Capitol building are inadvertent “whispering galleries” that enable people to hear conversations held on the other side of the room. Archaeologists have discovered acoustical arrangements like these dating back to 3000 BC. Many were used for eavesdropping.
The earliest electronic eavesdropping technologies functioned much like architectural listening systems. When installed in fixed locations—under floorboards and rugs, on walls and windows, inside desks and bookcases—devices like the Detectifone, a technological cousin to the more common Dictaphone, proved predictably effective. According to a promotional pamphlet published in 1917, the Detectifone was “a super-sensitive device for collecting sound in any given place and transmitting it by a wire thru any given distance to the receiving end, at which point the person or persons listening are able to hear all that is said at the other end … It hears everything, the slightest sound or whisper … The result is the same as though you were present in the room where the conversation was being carried on.”
Such devices were typically marketed as investigative tools for private detectives and law enforcement agencies. But manufacturers also envisioned more pedestrian uses for the technology: verifying the loyalty of business associates, corroborating statements made under oath, even monitoring patients in hospitals and insane asylums.
The devices that we now think of as “bugs” emerged much later. (In fact, the word bug didn’t gain traction as a nickname for a concealed eavesdropping device until after World War II.) During the late 1940s, electronic innovations made it possible for eavesdroppers to miniaturize listening technologies like the Detectifone. This made them easier to hide. It also freed them from the strictures of the built environment, dramatically expanding their reach.
Reports of an American bugging epidemic began circulating in the early 1950s—first, as glimpses of the man-made miracle of electronic miniaturization began to appear in newspaper exposés, trade magazines, and Hollywood films, and later as congressional subcommittees revealed scandalous eavesdropping tools on the floor of the US Senate. The numbers were impossible to substantiate, but by 1960 all accounts suggested that the bug had outstripped the wiretap as the professional eavesdropper’s weapon of choice. The electronic listening invasion had begun.
The middle section of The Eavesdroppers, a 1959 book by the University of Pennsylvania engineer Richard Schwartz, was intended to account for this new development in the world of electronic surveillance. Brusquely titled “Eavesdropping: The Tools,” Schwartz’s chapter took stock of the miniaturized listening devices that professionals were using in the field. In the process, he told a more disconcerting story about ordinary technologies turned against the society that had created them. There were induction coils that allowed eavesdroppers to listen to telephone conversations without making physical contact with telephone wires. A special brand of conductive paint, invisible to the unaided eye, could redirect phone signals to outside lines. There was a new class of microphones engineered to be smaller than sugar cubes and thinner than postage stamps. These could be secreted away in surprising locations: wall sockets, picture frames, packs of cigarettes. They transformed everyday items into covert listening machines.