From: Eric Murray <ericm@lne.com>
Date: Sat, 27 Jul 1996 09:21:48 +0800
To: bqm1808@is.nyu.edu (Brendon Macaraeg)
Subject: Re: "privatizing" phones?
In-Reply-To: <1.5.4.32.19960726085331.0067db88@is.nyu.edu>
Message-ID: <199607262311.QAA22874@slack.lne.com>
MIME-Version: 1.0
Content-Type: text/plain


Brendon Macaraeg writes:
> 
> Cpunks:
> 
> While shopping for a new phone recently, I came across
> two models (Toshiba and Uniden I believe) that
> have buttons to "privatize" you conversations. These
> were on no-cord models.

I have one of these, a Panasonic "Secure Guard" cordless.
It was on sale, I couldn't resist. :-)

It's a 46mhz analog model, newer phones use frequencies
in the 900mhz range and/or digital encoding.
The 900mhz range is one of those 'blocked' in most newer radio
scanners, this is required by law as of a few years ago.
Many scanners can have some or all of the locked-out
ranges restored by suitable modification (i.e. removing
a resistor).  Many of these mods are posted on the net.

> Does anyone have any idea
> on what these actually do? Can the phones  change
>  the frequency the call is on randomly
> so people can't tune into it?

The Panasonic I have doesn't change frequencies during the call
by itself, although you can do that by pressing a button.  The
"secure" feature does some sort of analog frequency-diddling
to make most of the sound transmitted between the phone and base unit
unintelligable.  I'm not a hardware type but I expect that
this isn't very hard to 'crack' given a bit of equipment.
I'm sure most HAM hobbiests could do so.   It only keeps your
conversations somewhat safe from the local snoops with scanners.

While most speech comes out pretty good, you can't have the 'secure'
feature on when you're attempting to navgate phonemail systems... it messes
up the DTMF tones just enough to make then unrecognizable to
many phonemail systems.

> I know cellulars offer something similar. 

Yea, that's more secure although if I remember right, nowhere
near unbreakable.  Why, then drug dealers and terrorists could
make phone calls and our great and wonderful law enforcement personell
would not be able to listen in on the perps.  Wouldn't want that
now, would we?

> Personally, I would never put much faith into
> something of this sort. 

Well, it's not "secure" but it's somewhat better than nothing.



-- 
Eric Murray  ericm@lne.com  ericm@motorcycle.com  http://www.lne.com/ericm
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