From: haynes@cats.ucsc.edu (Jim Haynes)
Newsgroups: alt.folklore.computers
Subject: Telephones (Re: What happened to "smart buildings"? and three tangents)
Date: 7 Jan 1993 22:17:57 GMT
Organization: University of California; Santa Cruz
NNTP-Posting-Host: hobbes.ucsc.edu


In article <C0Hysr.4oD@NeoSoft.com> claird@NeoSoft.com (Cameron Laird) writes:
>adventures in telecommunications was, "Well, The Phone
>Company doesn't want you using any equipment it hasn't ap-
>proved, because you might put a bad signal on the line,
>and hurt its switches."  Was there some technical reality
>behind this, or was it just polite language for AT&T to
>say, "Mine, all mine, and you can't do anything about it!"?
This is a long story that really belongs in one of the telcom newsgroups, but
From sometime in the late 1800s Theodore Vail who was Pres. of AT&T
at the time took a cue from United Shoe Machinery and decided that
the telephone compnay would own all the apparatus and lease it to
the customers.  Note in passing that this doctrine was also taken to
heart by Tom Watson, Sr. in IBM Corp some years later.  Now the telephone
companies being regulated public utilities, the rates they charge and the
terms and conditions of using the service all became matters of state law;
so the prohibition of customers attaching anything to the telephone network
had the force of law as well as being the policy of the company.  The only
exceptions were for private lines, where there were classes of service for
burglar alarms and radio and TV networks and various other things.  Now
there are some real potential problems is having just anybody connecting
things to the telephone wires.  You might unintentionally connect the
power line to the telephone line and cause a telephone lineman to get
shocked and maybe fall off a pole.  You might send an amplified signal
down the line such that it caused intereference to every other pair of
wires in the same cable.  You might get injured yourself if you happened
to have your hands on the telephone wire when the phone rang, because
they use 90 or more volts AC; you could get shocked and fall off a ladder
or something.  For private lines they had to assume the customer people
making connections knew more or less what they were doing and were able
to abide by the rules about what they could put on to the line.

In the 1960s a lot of things started happening.  People wanted to connect
computers and oddball terminals over dialed-up phone connections to avoid
the high cost of private lines.  The phone company responded by developing
a family of modems with telephones built in. This by the way was the origin
of the RS-232 interface, a way for the phone company and the business
machine manufacturers to agree on how they would connect to each other.
Then there was the Carterfone decision - a legal battle ending in a court
overturning the phone company's absolute ban on customers connecting to
the switched network.  At first the phone companies were allowed to demand
that a "network protection device" supplied by them be inserted between
the phone line and the customer equipment.  These devices typically
contained an isolation transformer, some varistors (level limiters),
and a relay to control a DC bridge on the phone line to control off-hook/
on-hook signaling.  Later court rulings allowed the customer to provide
the network protection circuitry built into the equipment, so long as it
met standards promulgated by the FCC.  The general thrust of the standards
is that an ordinary telephone needs no network protection device; after
all the telephone companies didn't supply one with the phones they supplied.
Something like a modem that is connected to the power line needs an isolation
transformer with good insulation resistance and balance, so that even
if lightning strikes the AC power line isn't likely to get connected to
the phone line, and that sort of thing.

Then there was the breakup of the Bell System, with one of the provisions
being that the local telephone companies couldn't stay in the phone leasing
business.  A follow-on to this is that the phone wiring in your house is
your own responsibility; the phone company provides service to a terminal
point typically located on the exterior wall of your house and you take it
from there.

There was a while that you were supposed to notify the phone company of
what kinds of things you had connected.  The reason goes back to methods
of testing telephone lines, manually and automatically - lots of phone
offices these days automatically test all lines at night.  With standard
phones the ringer is in series with a capacitor, so when DC is applied to
the line there is an initial surge of current as the capacitor charges,
and another surge when the DC polarity is reversed and the capacitor charges
the other way.  In the old days the telephone repair people would do this
testing watching a meter - if the meter kicks when polarity is reversed
and then goes to zero all is well.  If the meter doesn't go to zero then
the line is shorted or grounded.  If the meter doesn't kick then the
line is open somewhere.  I guess nowadays people plug and unplug phones
so much and new-fangled ringers don't need a big capacitor anyway that
the kick test is worthless and the companies have ceased to care that
you tell them what you have connected.  Unless you connect so many phones
with so much capacitance that their ringing machine can't handle the load;
but that's unlikely.
>
>Marginally related to that last:  really, it wasn't long ago
>that having a telephone that was mobile enough to be
>unplugged and plugged back in SOMEWHERE ELSE was an extrava-
>gance even on the psychological level.  I have a vague
>memory that, in some times and places (before WWI, Eastern
>Europe?), it was not unusual for The Telephone in a house
>to have its own room, that is, a cabinetwork arrangement
>that would remind us of a telephone booth--that's inside
>the house, right.  Am I remembering something real, or was
>this a dream?

One thing you might be remembering - I've seen pictures of very old
long-distance telephones that were built into a booth almost as big
as a closet.  Back before electron tube amplifiers were invented
there was a limit to how far you could talk on the telephone because
of signal losses in the wire; so to talk long distances you had to
get into a very quiet place to hear and be heard.  Even after electron
tube amplifiers were invented they were bulky and expensive and required
lots of maintenance, so the telephone companies didn't use them on
circuits where they thought you could probably hear well enough without
them.  Also the old telephone transmitters and receivers were a lot less
efficient than the modern ones - which says a modern telephone without
electronics will talk farther than an old one could.  Today of course
you can get telephones with amplifiers built in; and electronics is
so pervasive throughout the telephone network that you can't tell how
far you are talking by how weak the sounds are.  I'm not acquainted
with any old homes, and certainly not any with telephone booths, but
it seems like a reasonable thing one might do in building a house
around the turn of the century when you had a little experience with
how weak telephone sounds are, and if you have a bunch of noisy kids
or live in a noisy neighborhood, or if you are installing the phone
in a busy store or shop with machinery.

Some of the very old 'long distance' telephone transmitters had to
be mounted horizontally for best efficiency, so there were some very
ornate built-into-a-desk telephones designed for this service.  Being
an expensive service it probably justified an expensive telephone anyway.
-- 
haynes@cats.ucsc.edu
haynes@cats.bitnet

"Ya can talk all ya wanna, but it's dif'rent than it was!"
"No it aint!  But ya gotta know the territory!"
        Meredith Willson: "The Music Man"