Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!eplunix!raoul
From: raoul@eplunix.UUCP (Nico Garcia)
Newsgroups: sci.electronics
Subject: Part number identification, from Popular Electronics
Keywords: SK2086, phones
Message-ID: <1081@eplunix.UUCP>
Date: 24 May 91 18:23:15 GMT
Organization: Eaton-Peabody Lab, Boston, MA
Lines: 27

There's a design for a multiple line use detector in a recent issue
of Popular Electronics: page 21 of the July issue. Unfortunately,
one of the chips mentioned is the SK2086. As near as I can tell
from my latest ICMaster, it's a set of transistors. Unfortunately, the
pinout is different for different manufacturers. The diagram is
very unclear on the actual function of the chip. The article itself
describes the chip as opto-isolators. Can anyone out there identify
the manufacturer and actual function of the !@#$ thing?

Others may have noticed that in-use indicators appear everywhere all
the time. True: but ones that can be hooked in parallel with
your phones, *and draw no DC current in the on-hook state* are
rare. In series is easy, but that means tapping the phone line
before it gets spread around your house. Voltage dividers are easy too,
to get the signal down to something you can read easily: but that means
connecting the thing to ground somewhere (not a great idea) and
drawing current.

Of course, the designer of this circuit could be using an office
system, which doesn't care if you draw a little bit of DC: but then
it's not very useful for hooking up to Bell systems, is it? 


-- 
			Nico Garcia
			Designs by Geniuses for use by Idiots
			eplunix!cirl!raoul@eddie.mit.edu