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From: len@syssoft.com (Len Galasso)
Newsgroups: sci.electronics
Subject: Phones used as intercoms
Message-ID: <1990Nov12.181746.5465@syssoft.com>
Date: 12 Nov 90 18:17:46 GMT
Reply-To: len@syssoft.com (Len Galasso)
Organization: Systems & Software, Inc., Irvine, CA
Lines: 38



I live in a four-bedroom, split-level house which has at least one phone
jack in each room.  What I'd like to do is to allow the phone "network"--
if you will--act like a local intercom when it isn't being used as a
regular phone system.  More specifically, I'd like to be able to somehow
isolate the system from the "Phone Company" and by the use of a special
ringing sequence which is obviously non-standard (at least for our region),
say, a burst of short ringing tones, enable someone in the house to pick 
up the phone in any room and carry out a conversation.

The way this came about is that I was going to install some sort of an
intercom, using either the power-line carrier or FM wireless variety and
I got to thinking that I *already* have an intercom system: the
telephones.  Any user would not have to learn how to yet another piece
of electronic equipment.

Now the details.  When the system is being used as an intercom, outside
callers should get a busy signal.  To envoke the "special ringing sequence",
the user should have to just hit a special series of keypad commands--say
#*55--and the whole system would ring.  Thus any phone in the whole house 
could be picked up and the conversation could take place.  

I suppose some sort of intelligent isolation device would have to be placed
between the main feed from the Phone Company into my house.  This would have
to sense the command set defined--at this point only the special ring. And
then when the "intercom mode" is finished it would reconnect the whole system
back to Ma Bell.

I would like some input on this concept in terms of what it would take to
build something like this.  I am not looking for schematics--just ideas.

+------------------------------+-------------------------------------------+
|  Len Galasso                 | "Just a machine to make big decisions     |
|  Systems and Software Inc.   |  Programmed by fellows with compassion    |
|  len@syssoft.com             |  And Vision"                              |
|  (714) 833-1700              |    Donald Fagen, "IGY", _The_Nightfly_    |
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