I think you missed my point Russel. (This seems
to happen a lot. Wonder why ...)

Safety and isolation should be a design goal
in *real* product from the beginning - not an
after thought ... even if the 'product' never
sees the light of day in production the daily
use of something built by an by an experimenter
could one day prove fatal ...

That's my point.

NEVER underestimate what Mother Nature, physics
and other people (perhaps making mistakes while
doing high-voltage line work on a pole somewhere!)
can throw at at you. Never underestimate ...

When you're connecting to a "wire" that runs 15,000
some feet to a telco 'switch' via both underground and
above ground paths - there is plenty of potential
('scuze the pun) for trouble when least expected.

It's *one* thing to fool around with wiring that resides
*solely* on one's own premises - it's something else
quite again when a twisted pair runs onto your property
and into one's lab from afar ...

RF Jim


----- Original Message -----
From: "Russell McMahon" <apptech@PARADISE.NET.NZ>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, August 01, 2002 4:43 PM
Subject: Re: [EE]: Telephone monitor


> > Doesn't anybody think safety and or "isolatin
> > of the line" from possible human contact anymore?
> > That used to be a consideration (BUT with the
> > declining cost of technology I fear safety has
> > taken a back seat to features and bottom-line
> > cost).
>
> Rest assured that this is still required just as much as ever - at least
in
> this country where there are regulatory standards to meet, as I noted.
> I assume that most other countries also haven't thrown away the rule book
in
> the face of the declining cost of technology - certainly the Telcos won't
> have as the purpose of isolation is to protect both people from lines and
> lines from people. The  latter is more important to the Telco's Ops
manager
> and the former to the Telco's lawyers.
>
> As I noted, lest the point has somehow been missed, this was just a
> discussion of the principles concerned - a starting point for someone to
> learn something instead of just going down the road and buying an existing
> technologically encheapend one for a fraction of the price of a
> roll-your-own.
>
> None of the techniques mentioned so far by any respondent actually
*demands*
> a
> lack of 'isolatin of the line' - what one does in the privacy of one's own
> breadboard and how this is implemented in a product are different. Safety
> during development is, of course,  important but the final circuitry can
> float in isolation from the real world if needs be.
>
>
>         RM
>
>

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