Re: Husband Automation ?

["the_home_automator <db@xxxxxxx>" <db@xxxxxxx>]

--- In ukha_d@xxxxxxx, "Paul Gale" <p-gale@b...> wrote:
> If you want some kind of hands free duplex (i.e. both talk at the
same
> time) system - won't you have to have some circuitry to prevent
feedback
> like most hands free phones have?
>

Oh absolutely.  But I assumed (possibly wrongly?) that for a home
built job with a few components, a half duplex, push to talk
mechanism would suffice.

To do full duplex needs more electronics; the high-end kit uses DSPs
and black magic.  At the more affordable end of the world, a
"hybrid"
is what is needed.  This basically subtracts the mic signal from the
mixed signl, an thus just the incoming (ie from the other end) audio
is heard, and feedback cancelled.  With careful setup this work, but
you do need to get near the mic to keep the gain requirements down!

he other trick is to use a VOX (voice operated switch) mechanism, as
many handsfree phones do.  Its near enough full duplex for most
folks...

David


http://www.automatedhome.co.uk
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