From: peter.m@insane.apana.org.au (Peter Tryndoch)
Sender: FredMail@insane.apana.org.au
Path: cantaloupe.srv.cs.cmu.edu!crabapple.srv.cs.cmu.edu!bb3.andrew.cmu.edu!news.sei.cmu.edu!cis.ohio-state.edu!zaphod.mps.ohio-state.edu!uwm.edu!cs.utexas.edu!uunet!munnari.oz.au!ariel.ucs.unimelb.EDU.AU!werple.apana.org.au!insane!FredMail
Newsgroups: sci.electronics
Subject: Telephone On Hook/Off Hok
Message-ID: <734953838.AA00506@insane.apana.org.au>
Date: Thu, 15 Apr 1993 23:34:03
Lines: 17

AllMichael CovingtonTelephone on hook/off hok

MC>From: mcovingt@aisun3.ai.uga.edu (Michael Covington)
MC>Organization: AI Programs, University of Georgia, Athens
MC>Aye, there's the rub -- if you draw enough current to light an LED, th
MC>equipment at the phone company will think you've gone off hook.
MC>In the on-hook state you're not supposed to draw current.  

Ok lets have some calculation here: Going by Australian standards, which I 
presume might be similar to other countries ( If not, lets have some 
input) a phone uses 600ohm to loop a 48V line = 80mA. A standard LED 
drains 20mA. So what is the actual loop current required for an "off hook" 
indication, do you know?

Cheers 
Peter T.

