Devices exist which, by sending an electrical impulse of ultrasonic frequency through a telephone circuit by tapping, will permit remote surveillance of any office in which a telephone is located by utilizing the telephone microphone as a pick-up. Such eavesdropping may be accomplished without additional wires and is possible even though the handset is in a “hung-up” position.

Below, you will find thousands of pages archived from the FBI on ultrasonic listening devices, wiretapping, violations, and countermeasures.

Document Archive

 Ultrasonic Listening Devices / Wiretapping, 1945 – 1989 (80-HQ-760) – Release #1 – [1,064 Pages, 200.1MB]

 Ultrasonic Listening Devices / Wiretapping, 1945 – 1989 (80-HQ-760) – Release #2 – [8 Pages, 2.0MB]

 Wiretapping Violations (139-HQ-1) – Release #1 – [218 Pages, 140MB]

 Wiretapping Violations (139-HQ-3) – Release #1 – [37 Pages, 2.5MB]

 Countermeasures (80-HQ-805) – Release #1 – [2,666 Pages, 121.8MB]

 Countermeasures (80-HQ-805) – Release #2 – [6 Pages, 0.5MB]

Countermeasures (80-HQ-805) – FBI Release – Other Government Agency Material (CIA, FTC and SEC) [31 Pages, 1.8MB]

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