SIGSALY

SIGSALY exhibit at the National Cryptologic Museum

SIGSALY (also known as the X System, Project X, Ciphony I, and the Green Hornet) was a secure speech system used in World War II for the highest-level Allied communications. It pioneered a number of digital communications concepts, including the first transmission of speech using pulse-code modulation.

The name SIGSALY was not an acronym, but a cover name that resembled an acronym—the SIG part was common in Army Signal Corps names (e.g., SIGABA).[1] The prototype was called the "Green Hornet" after the radio show The Green Hornet, because it sounded like a buzzing hornet, resembling the show's theme tune, to anyone trying to eavesdrop on the conversation.[2]

  1. ^ Cite error: The named reference autogenerated1 was invoked but never defined (see the help page).
  2. ^ "Vox Ex Machina". 99% Invisible. Retrieved 2022-03-28.