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SRR-90
Surveillance receiver - under construction

SRR-90 was a surveillance receiver for the reception of a several types of covert listening device (bug), developed around 1975 by the Dutch Radar laboratory (NRP) for the US Central Intelligence Agency (CIA), as part of a long-term research contract codenamed Easy Chair. The SRR-90 was the enhanced version of the SRR-91. It had a modular design and was available in two models.
 
...   
SRR-90B (flat model)

 
Improvements over SRR-91
The SRR-90 has all characteristics and features of the SRR-91, plus the following:
 
  • Two case variants: upright (A) and flat (B)
  • Automatic frequency correction (AFC)
  • 6 preset channels
  • Automatic selection between '56' (RP) and '91' (DP) signals
  • Relay output, activated when locked onto a proper signal
Models
  • SRR-90 A
    Upright version with all controls at the front.

  • SRR-90 B
    Flat version with all controls at the top. Total height 60 mm. Suitable for operation inside a standard briefcase.

SRR-90 A
...   
SRR-90A receiver (upright model)

 
SRR-90A receiver (upright model) Front panel SRR-90A without the cover Modules inside the SRR-90A Rear view (cover removed) Expansion connector Input and output sockets Frequency dial

 
SRR-90 B
...   
SRR-90B (flat model)

 
SRR-90B (flat model) SRR-90B with open lid Close-up of the plug-in modules SRR-90B seen from the rear (with open lid)

 
Confusion
Although its model number suggests otherwise, the SRR-90 was developed and produced about one year after the SRR-91. The reason for this is the fact the SRR-91 was initially known as the SRR-91 Mk I and the enhanced version, which would be produced later, as the SRR-91 Mk II. However, when the SRR-91 Mk II was ready for release, the CIA decided to rename it SRR-90.
 
Further information

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Crypto Museum. Created: Friday 10 March 2017. Last changed: Sunday, 23 April 2017 - 13:59 CET.
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