Voice over data

[rishab@dxm.ernet.in]

Eric Hughes wrote:
>    the great voice-over-data protocols and products introduced by
>    Intel, Rockwell, ZyXEL and others at Comdex which will make
>    Voice-PGP so much easier
> 
> As I understand these voice-over-data products, the voice goes over
> analog, added to the modem signal.  The modem signal is interpreted,
> and then reconstructed and subtracted from the incoming signal,
> leaving voice.  Very clever, but insufficient for secure phones.

I don't think that's how they do it. As far as I know, most methods multiplex
digitized audio with the data. One system used by some people in India provides
a dynamic combination of fax, (digitized) voice and data, depending on the
throughput - eg vox/9.6 data if 14.4kbps, fax as well if 19.2, etc.

While Intel and others are proposing standards, ZyXEL does it with software
along with a voice card or possibly RJ11 input. A friend of mine saw a demo
of it at Comdex, on an old 1496E (16.8 kbps zyxel to zyxel). The new v.34 does
28.8k - lots of room for clear digitized voice and high speed data.

This is exactly why I thought it would make secure voice easier, if not secure
phones (who wants to lug a modem and PC around as a 'handset'?).

I'll be testing some Onetics Rad VFAST modems this week, which apparently do
digitized voice over v.34 as well.

-----------------------------------------------------------------------------
Rishab Aiyer Ghosh             "Clean the air! clean the sky! wash the wind!
rishab@dxm.ernet.in                   take stone from stone and wash them..."
rishab@arbornet.org
Voice/Fax/Data +91 11 6853410  
Voicemail +91 11 3760335                 H 34C Saket, New Delhi 110017, INDIA