Homepage
Crypto
Spy radio
Burst encoders
Intercept
Covert
Index
Glossary
Cameras
Recorders
Radio
Bugs
Microphones
Concealments
Lock picking
Stories
Radio
PC
Telex
People
Agencies
Manufacturers
• • • Donate • • •
Kits
Shop
News
Events
Wanted
Contact
About
Links
   Click for homepage
SRT-105
Covert listening device with SC audio masking - under construction

SRT-105 was a covert listening device (bug), developed in 1974 by an unknown party 1 for the US Central Intelligence Agency (CIA). The device uses a sophisticated audio masking scheme, known as subcarrier modulation (SC), with additional baseband noise injection (SC/Noise).

The measures just xxx x xxx mm and should therefore be considered subminiature for the era. It worked by frequency modulating (FM) the intercepted audio onto a 40 kHz subcarrier (SC), which was then frequency modulated onto the 300 MHz carrier. As an extra masking measure, a strong (random) noise signal, was injected into the device's baseband audio channel, to defeat the squelch of an ordinary surveillance receiver.

The image on the right shows the SRT-105 as it was presented in the tiny manual that came with it.
  

Although the use of Subcarrier Modulation (SC) as an audio masking scheme was really sophisticated for the era, it was easily defeated by Audiotel's Scanlock Mark VB bug tracer.

  1. From surviving documents it is known that unlike many other bugging devices, this particular model was not developed and manufactured by the Dutch Radar Laboratory (NRP). However, the NRP did developed a suitable surveillance receiver for it, under the Easy Chair research contract.

Documentation
  1. Instruction Manual SRT-105
    October 1974.
References
  1. Anonymous source, SRT-105 instruction manual
    Retrieved March 2017.
Further information
Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
Crypto Museum. Created: Thursday 09 March 2017. Last changed: Tuesday, 13 June 2017 - 07:28 CET.
Click for homepage