Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Data Over Voice
Message-ID: <1989Dec8.171522.3912@utzoo.uucp>
Organization: U of Toronto Zoology
References: <8912061817.AA28752@en.ecn.purdue.edu>
Date: Fri, 8 Dec 89 17:15:22 GMT

In article <8912061817.AA28752@en.ecn.purdue.edu> steele@en.ecn.purdue.edu (Richard Steele) writes:
>Here at Pudue U., we now have access to something called data over voice
>(DOV) units.  These are small boxes, about the size of a regular modem,
>that gives the user a 9600 bps asynchronous data line to the University
>computer.  Not only is the bugger faster than a modem, _but it leaves
>the phone free for regular use_...
>Question:  How would something like this work?  The phone company _does_
>need to make some changes to their central switch (or something like that...

The wires connecting your phone to the phone company have lots more bandwidth
than voice can use, as witness folks who are using similar wiring (admittedly
over shorter distances) to carry 10Mb/s Ethernet signals.  The bandwidth
limitations on normal voice calls generally come in the switching gear and
long-haul connections, not in the local wiring.  So *if* your phone company
(or your university, if it has its own phone system) is willing to put a
box on the other end of those wires, and connect that box to something, it's
not difficult for something on your end to use some of that bandwidth to
talk to said box digitally.  With a bit of care in design, it can avoid
interfering with the miniscule fraction of the bandwidth normally used for
voice.  Presto, data and voice on the same wires.

The hard part is convincing the phone company to put that box on your wires,
and put matching boxes on the wires of the places you'd like to talk to, and
connect all the boxes together, and not charge you two arms and a leg for it.
-- 
1233 EST, Dec 7, 1972:         |     Henry Spencer at U of Toronto Zoology
last ship sails for the Moon.  | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
