AudioLock: video and audio encryption system.
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AudioLock Digital Audio Scrambling Upgrade for ViewLock II



Audiolock II upgrade for Viewlock II allows up to two audio channels to be encrypted together with the video. With no size increase over the standard video only unit, Audiolock II is highly compact and offers complete protection for video and audio surveillance links.

Audiolock II converts the incoming audio to an encrypted digital bit stream and adds this audio data to unused video lines. This technique is a robust and highly secure method of transmitting the audio over the link.

Audiolock II uses advanced digital audio compression, resulting in excellent signal to noise performance. Indeed, Audiolock II provides near broadcast quality audio, vastly superior to the traditional sub-carrier audio channels used by video microwave links.

AudioLock II Upgrade





System Overview

Audio Lock Application Diagram
AudioLock Application Diagram

With the Audiolock II upgrade, the video is connected in the normal way to the Viewlock II, however, audio is presented to the encoder rather than the transmitter. The Audiolock encoder then combines the audio within the scrambled video feed ready for secure transmission. At the receive site, the decoder extracts the audio to provide a clear output. Audiolock is configurable for one channel of 14 kHz bandwidth or two channels of 7 kHz bandwidth.



Connection to AudioLock
Connection to AudioLock


Outline Specifications  
Scrambling method Digital audio data sent over video
Audio input /output level (nominal) 0 dBU i.e. 2.2 V peak to peak (unbalanced)
Max audio input / output level +5 dBU (approximately 4 V peak to peak)
Audio input impedance > 10kR
Audio output impedance < 100R
Number of audio channels 1 or 2 (DIP switch select)
Audio bandwidth (mono) 30 Hz to 14 kHz (+1, -3 dB)
Audio bandwidth (stereo) 30 Hz to 7 kHz (+1, -3 dB)
Signal to noise (wrt 0 dBU input) >60 dB (weighted)
Distortion @ 0 dBU , 1 kHz < 1%
Video data lines used Lines 5-16 / 318-329
Audio Compression Equivalent to 16 bit audio via adaptive differential pulse code modulation (ADPCM) giving 4 to 1 compression.



Due to continual product development Ovation Systems reserve the right to change specifications without notice. E&OE.