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From: gbell@sdcc13.ucsd.edu (Greg Bell)
Newsgroups: sci.electronics
Subject: Re: Drawing DC phone current
Keywords: SK2086, phones
Message-ID: <20017@sdcc6.ucsd.edu>
Date: 1 Jun 91 19:56:34 GMT
References: <8053@nst> <1084@eplunix.UUCP> <1991May29.084859.5324@specialix.co.uk>
Sender: news@sdcc6.ucsd.edu
Organization: University of California, San Diego
Lines: 23

In article <1991May29.084859.5324@specialix.co.uk> stevem@specialix.co.uk (Steven Murray) writes:
>
>You used 2700 ohms - but the off-hook voltage was something like 18 volts -
>thats not 4 milliamps.   Just leave the 4 milliamps bit for a moment, try
>a resistor of value 22k.  Its still not 'proper' but I think you will find
>it works.  I'm not suggesting you do this on anything but your own private
>telephone exchange :-)
> 
>

Never mind the fact that if you design something that places a
resistive load across the phone line, and later your phone rings,
the current you're drawing jumps because the phone line ring voltage
is higher than the on-hook voltage.  So, your resistor answers the
phone on the first sign of a ring, then drops it...



-- 
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  Who:  Greg Bell                            Address:  gbell@ucsd.edu
 What:  EE hobbyist and major                  Where:  UC San Diego
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