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From: psfales@ihlpl.UUCP
Newsgroups: sci.electronics
Subject: Re: Question about multi-switched lights
Message-ID: <1947@ihlpl.ATT.COM>
Date: Thu, 26-Mar-87 10:51:36 EST
Article-I.D.: ihlpl.1947
Posted: Thu Mar 26 10:51:36 1987
Date-Received: Sat, 28-Mar-87 04:59:16 EST
References: <1922@ihlpl.ATT.COM> <562@puff.WISC.EDU> <3972@fritz.UUCP> <18002@ucbvax.BERKELEY.EDU>
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 27
Summary: How to do it with lights.

In article <18002@ucbvax.BERKELEY.EDU>, albert@ucbarpa.Berkeley.EDU (Anthony Albert) writes:
> I realized that this is the same type of circuit which is used
> to turn on stairway lights from the top and bottom of the stairs.  This must
> be a fairly simple circuit, but I can't figure out how it's done (without
> taking it apart anyway).

This is quite simple once you see it, but it was a revelation to me when
I first figured it out:


	Switch A	    Switch B

	   --------------------
	  /			
---------o			o---------- Light -------
|			       /			|
120VAC	   --------------------				|
|							|
---------------------------------------------------------

A similar system should work for an extension telephone.

-- 
Peter Fales		UUCP:	...ihnp4!ihlpl!psfales
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