Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ukma!tut.cis.ohio-state.edu!att!cbnewsc!jgk
From: jgk@cbnewsc.ATT.COM (joseph.g.klinger)
Newsgroups: sci.electronics
Subject: Re: Using "Free" telephone power
Message-ID: <666@cbnewsc.ATT.COM>
Date: 3 May 89 14:37:55 GMT
References: <636@serene.UUCP> <920@snjsn1.SJ.ATE.SLB.COM>
Reply-To: jgk@cbnewsc.ATT.COM (joseph.g.klinger)
Organization: AT&T Bell Laboratories
Lines: 33

Newsgroups: sci.electronics
Subject: Re: Using "Free" telephone power
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References: <636@serene.UUCP> <920@snjsn1.SJ.ATE.SLB.COM>
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Reply-To: jgk@cbnewsc.ATT.COM (joseph.g.klinger)
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In article <920@snjsn1.SJ.ATE.SLB.COM> greg@sj.ate.slb.com (Greg Wageman) writes:
>In article <636@serene.UUCP> gbell@pnet12.cts.com (Greg Bell) writes:
>>
>>I'm still amazed at how phones run entirely off the phone line power.  They
>>have lit dials, and audio amplifiers... and I had trouble lighting an LED!
>>(trouble means the phone company equipment gets loaded down enough that it
>>shuts off your line for a while!).  
>
>Please note that the (Western Electric) telephones (e. g. "Princess")
>with lighted dials are supplied 6 VAC by a small line transformer
>which is typically connected to the black and yellow "unused" wires in
>the phone jack.  

I have an AT&T 1300 feature telephone which only has connections to
tip and ring (I took it apart), no transformer, no yellow/black pair.
It also has two high intensity (and obviously high efficiency) LEDs which 
light the translucent pushbuttons when the phone is off hook,
drawing current from the telco line.  It's a current design, 1986.

Joe Klinger
att!iexist!jgk