Xref: utzoo sci.energy:3731 sci.electronics:16735 sci.physics:16228
Path: utzoo!utgpu!cunews!software.mitel.com!meier
From: meier@Software.Mitel.COM (Rolf Meier)
Newsgroups: sci.energy,sci.electronics,sci.physics
Subject: Re: solar cells
Message-ID: <5902@healey>
Date: 4 Jan 91 14:31:59 GMT
References: <1991Jan3.072059.20842@loop.uucp>
Organization: Mitel. Kanata (Ontario). Canada.
Lines: 21

In article <1991Jan3.072059.20842@loop.uucp> keithl@loop.uucp (Keith Lofstrom;;;628-3645) writes:
>30% of power use.  I saw a paper once on a smart power controller for the
>off-hook detection for telephones;  this circuit saves about 3 watts per
>phone.  There's a lot of phones out there.  So why waste all that silicon

I hate to be picky in an otherwise good posting, but phones use much less
power than that.  In the on hook state, there is of course no power being
supplied.  Off hook, the average loop draws about 40 mA, with the CO
voltage of about 50 V, so the CO supplies about 2 W.  Most of that is
dissipated in the CO and the loop; a phone requires about 1/4 W to
function, but typically dissipates about 1 W since most loops are short.

Proprietory digital phones (and tomorrow's ISDN phones) may actually
use more power, because the digital circuitry needs to be continuously
active in order to sense signaling information.  For highly functional
digital sets, an ac adapter is often required because you can't
guarantee supplying more than 1 W to the end of the loop.

___________________________________________________________________
Rolf Meier					Mitel Corporation