Article View: sci.electronics
Article #18006How do you build phone off-hook indicator
From: ACM
Date: Tue, 08 Sep 1987 17:14
Date: Tue, 08 Sep 1987 17:14
22 lines
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1560 bytes
Ok you wizards out there. I have 4 phones (on one line) in my suite
which are being used by 6 people. Obviously there is some contention
for phone-time. It's a pain to have to pick up the phone (and bother
someone) to see if someone is on the line.
Now, I know there is a voltage differential between on-hook and
off-hook (I believe it's 24 volts on-hook and 10 off-hook but this is
purely from memory and I could be wrong). How can I build a simple
circuit to light an LED when the voltage drops? I'd prefer the
simplest curcuit possible that's pretty reliable.
Thanx for any help. Please email replies to madd@bucsb.bu.edu (or if
that doesn't work try acm@bu-cs.bu.edu or if that doesn't work just
post it although I don't read this group often, being a software
person).
jim frost
madd@bucsf.bu.edu
madd@bucsb.bu.edu
"But God favors drunks, small children, and the cataclysmically stoned...."
-- Stephen King, _It_
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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!mnetor!uunet!seismo!ut-sally!husc6!bloom-beacon!bu-cs!acm From: acm@bu-cs.BU.EDU (ACM) Newsgroups: sci.electronics Subject: How do you build phone off-hook indicator Message-ID: <12660@bu-cs.BU.EDU> Date: Tue, 8-Sep-87 13:14:44 EDT Article-I.D.: bu-cs.12660 Posted: Tue Sep 8 13:14:44 1987 Date-Received: Wed, 9-Sep-87 05:35:46 EDT References: <414@gtx.com> <4046@utai.UUCP> Reply-To: madd@bucsb.bu.edu Organization: ODO (Organization for the Disorganization of Organization) Lines: 22