Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!agate!e260-3b.berkeley.edu!128a-3db
From: 128a-3db@e260-3b.berkeley.edu (Jonathan Dubman)
Newsgroups: sci.electronics
Subject: Sensing telephone off-hook
Keywords: sensor telephone off-hook
Message-ID: <22901@agate.BERKELEY.EDU>
Date: 11 Apr 89 04:44:14 GMT
Sender: usenet@agate.BERKELEY.EDU
Reply-To: 128a-3db@e260-3b.berkeley.edu (Jonathan Dubman)
Distribution: usa
Organization: University of California, Berkeley
Lines: 16

I realize this was asked recently, but I just started reading this newsgroup
and I think I missed some of the responses.

We need a sensor circuit to determine whether a telephone line is off-hook.
I have lots of parts handy and I suspect it is a relatively simple
voltage-range detector circuit, but I'm not sure of the voltages.  Is it
this simple?

The reason we need this sensor is to prevent somebody from interrupting
a download in progress.  It would be more fun and slightly cheaper to build
rather than buy if the circuit is indeed simple.

Thank you very much!

	-Jonathan Dubman
	128a-3db@web.berkeley.edu