Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!unmvax!ncar!tank!shamash!com50!pwcs!minnow!ron
From: ron@minnow.sp.unisys.com (Ron Burns)
Newsgroups: sci.electronics
Subject: Need a simple telephone off-hook sensor
Message-ID: <1315@minnow.sp.unisys.com>
Date: 24 Mar 89 21:02:48 GMT
Reply-To: ron@minnow.UUCP (Ron Burns)
Distribution: usa
Organization: Unisys Corporation - Roseville, MN
Lines: 33


I have got a small microcomputer board running my home weather station, and
I would like to use one of the serial lines to go to a modem so I can 
periodically dial up my computer here at work and transfer current weather
data.  

This does not present a problem, except that when someone is home, I want 
to be able to sense whether the phone is off the hook at another extension
so as not to slam an earful of phone dialling tones into someone's ear.

This in itself is enough, I guess, but it would be great if the circuit
was phone line powered, so that I could put a copy of this circuit on the
other extension, so an LED would go on, indicating that the computer was on
the phone, wait a moment for it to hang up.

the requirements seem simple:
	1)  TTL compatible output indicating phone off hook at extension
		or local phone jack.
	2)  No interference with normal phone operation.
	3)  (optional) Phone line powered to allow use at other extension.

Can someone out there help me with this??  Telephone circuits are just a  
mystery to me, even though this seems fairly simple.

Thanks a lot!!
-Ron



-- 
Ron Burns              
Unisys Corporation  UUCP: ...!amdahl!ems!minnow!ron   
Phone:(612)635-6927 CSNET: ron@minnow.SP.Unisys.Com