harmonica bug

plural harmonica bugs

1. An electronic eavesdropping device (bug) that attaches to a landline telephone and is activated or deactivated by a specific tone. When activated, it prevents the telephone from ringing but activates its microphone to transmit to another telephone at a remote location.

   The misplaced telephone receiver suggests they may have left a harmonica bug.

   1985, Vernon Tom Hyman, Giant Killer, page 78

   3 more examples

   The most interesting device for tapping a telephone, though, is still the old reliable “harmonica bug,” which was invented in the early sixties by an electronics wizard from Lower Manhattan, Emanuel Mittleman.

   1975, Alan LeMond, Ron Fry, No Place to Hide, page xii

   Whoever invented the harmonica bug realized that it's nearly impossible to find a bug that isn't operating, so he devised one that can be turned on and off by remote control.

   1975, United States. Congress. Senate. Committee on the Judiciary, United States. Congress. Senate. Committee on the Judiciary. Subcommittee on Constitutional Rights, Surveillance Technology, page 18

   It is, of course, tough to find a bug that isn't operating, which is at the heart of the harmonica bug principle.

   1982, Sonny Kleinfield, The Biggest Company on Earth: A Profile of AT & T, page 240

   Synonyms: infinity transmitter