31 July 2015

Harris AVS (Analogue Voice Security)

Discussing about an odd MS 188-110 App.B sample found in the web,  KarapuZ sent me a recording with a "combined" of signals in which are visible not only the 39-tone signal but also some Harris vocoder (AVS) segments. The ending ALE segment, once decoded, reveals the Roumenian Police network as source: [TO ][1P ][TWS][SIB]

Harris AVS
I take this opportunity to speak briefly about it. The Harris AVS (Analogue Voice Security) is a not-synced scrambler that use 24 subchannels and spreads about a  2700 Hz band. A detailed analysis can be read in the radioscanner.ru forum http://signals.radioscanner.ru/base/signal111/
Harris offers both digital encrypted and analog scrambler systems for COMSEC, below their short introduction to the AVS system: "In voice communications systems that do not require extremely high security, you can protect against casual eavesdropping by scrambling. Scrambling, as an analog COMSEC technique, involves separating the voice signal into a number of audio sub-bands, shifting each sub-band to a different audio frequency range, and combining the resulting sub-bands into a composite audio output that modulates the transmitter."

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