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RCA
  
MI-7181
Speech inverter - this page is a stub - wanted item

MI-7181 was a secure speech device, also known as a speech inverter or a frequency domain voice scrambler, introduced around 1939 by the Radio Corporation of America (RCA) in Camden (New Jersey, USA). The device was suitable for use of HF radio links and — when combined with the MI-7182 Hybrid Unit — over regular analogue telephone lines (PSTN).

Documentation
  1. Speech-Inversion Equipment MI-7181 and Hybrid Unit MI-7182 1
    IB-30011. RCA. No date.
  1. Documentation kindly provided by Herman Van Rees [1].
References
  1. Herman van Rees — MI-7181/MI-7182 manual - THANKS !
    Crypto Museum, 15 January 2026.
Further information
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© Crypto Museum. Created: Thursday 19 February 2026. Last changed: Thursday, 19 February 2026 - 13:58 CET.
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