From: mcovingt@aisun3.ai.uga.edu (Michael Covington)
Subject: Re: Telephone On Hook/Off Hok
Nntp-Posting-Host: aisun3.ai.uga.edu
Organization: AI Programs, University of Georgia, Athens
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In article <734953838.AA00506@insane.apana.org.au> peter.m@insane.apana.org.au (Peter Tryndoch) writes:

>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?

Up to 60 microamperes  =   on hook

Over something like 10 mA  = off hook

In between = defective line, and the phone company comes looking
              for leaky insulation.



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