TELECOM@Usc-Eclb.ARPA (04/04/83)
TELECOM AM Digest Sunday, 3 April 1983 Volume 3 : Issue 20
Today's Topics:
DTMF->Ascii Conversion
Long-Distance Access Charges (2 Msgs)
Is Local Measured Service Fairer?
An Anecdote From The History Of Telephony
Calling Card Query
Multi-Device Hookup With Modems
Data Conference Calls
Measured And Unmeasured Service In New Hampshire (2 Msgs)
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From: "REX::MINOW c/o" <SCHRIESHEIM.MITTON at DEC-Marlboro>
Date: 3-JAN-1983 20:54
Subj: Submission -- DTMF->Ascii conversion
Several recent Human Nets messages have discussed generation of Ascii
by means of a DTMF (Touch-Tone) keypad. I've done a bit of work on
this and hope the following might be of interest to Telecom readers:
First, holding multiple buttons down at the same time probably won't
work in the real world. There are several companies offering DTMF
decoders (coupled with FCC approved telephone line interfaces) which
are generally set to reject single frequencies (as required by the
AT&T specifications).
Using multiple keystrokes seems to offer the best of a bad situation
(clumsy, but workable). Several such systems have been done. For
example, there is a very nice automated weather forecast system using
synthesized speech and DTMF control done by the FAA. Also, Lauren
Weinstein implemented a telephone interface to Unix at UCLA, using the
Unix speak program (text to speech for a Votrax ML1) and a Bell 407
telephone line interface. With much help from Lauren, I implemented a
telephone interface to RSTS/E about 3 years ago using the NRL text-
to-speech system. All three systems used essentially the same DTMF to
Ascii encoding method:
Letters are entered by pressing the button containing the letter,
followed by a button indicating which of the three (left, middle, or
right) letters is desired. Thus ABC would be 21, 22, 23. The FAA
system accepted only 1/2/3 for the second button, while the other
systems allowed "any number in that column". Thus, on the UCLA and
DEC systems, "HUMAN" could be encoded 45, 88, 64, 21, 65.
There are two letters missing from the keypad. The DEC system put
them on the '1' key as "<space>QZ" (The other systems used something
similar, but I felt that 11 was a good way to encode space.)
Digits were encoded in the DEC system by combining them with the ZERO
key. Since I could never remember whether the zero came first or
last, my program accepted either encoding.
Now, the fun begins... The SHARP key was used for control characters:
#1 Z == end of file (CTRL/Z at Dec), #2 C == CTRL/C,
#3 D == Delete (rubout), #6 O == CTRL/O (Cancel output)
#7 R == Retype line (CTRL/R) #7 U == CTRL/U (Delete line)
## == Carriage return.
The STAR key was used for control functions. Lauren and I implemented
case shifts and locks as yhwell as numeric, control, and 8-bit octal
input. There was also a punctuation mode (courtesy of Lauren) whereby
the next three button pushes were interpreted as a graphic character.
For example, 365 (DOL) for '$', 758 (PLU) for '+', 277 (BSP) for
backspace, etc. Many characters had several definitions. For example
'<' was both 522 (LAN) and 535 (LES). Finally, there were a few
predefined messages:
910 Logout
911 MAIL
990 run games:dungeon
While it was a nice toy and a fun demo, and once in a while was very
useful, the amount of button pushing you had to go through was
extremely frustrating. Also, the quality of the Votrax voice was not
satisfactory for anything more than games playing.
I'd appreciate hearing with anyone with ideas on improving this
system; especially someone who would have no other access to a
computer.
Finally, the IBM voice mail system uses the keypad to enter user
names. They use the digits (MINOW would be entered 64669) as a hash
function. On the IBM system, Q is on the 7 key (PQRS) and Z on the 9
key (WXYZ).
Martin Minow
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Date: 1-Apr-83 23:19:29-EST (Fri)
From: cbosgd!mark@Berkeley (Mark Horton)
Subject: Re: Access Charges
>From the April 1 Columbus Dispatch: "Ohio Bell rate bid is blasted"
(This is an excerpt from an article quoting William Spratley of the
Ohio Consumers' Counsel, in response to a requested Ohio Bell rate
hike.)
Ohio Bell's announcement that it is seeking a 46 percent rate increase
for residential customers "is highly misleading", Spratley said. Ohio
Bell officials said the basic service charge of $12.95 will be
increased to $18.80 a month, and the $1.50 rental fee for a telephone
would remain the same. ... However, another $8 in new charges for
long distance service will be added to everyone's bills. That will
raise the current $14.45 basic service charge to $28.30, if the new
rates are approved by the PUCO, Spratley said. "That is a 96 percent
increase." ... People who now pay $9.75 for message rate service would
pay $21.50 a month - a 121.5 % increase. Those who use measured
service would see their $7.30 basic charge increased to $18 a month,
for 147% increase.
...
Half the $8 charge is being sought by Ohio Bell to pay for the service
of long-distance calls within Ohio. The FCC is expected to add on
another $4 charge to subsidize Ohio Bell's service for long distance
calls to other states.
Ohio Bell will lose its current subsidy next January when AT&T is
forced to divest itself of local telephone companies such as Ohio
Bell. Spratley said only those who make lots of long distance calls
would benefit from Ohio Bell's proposal. [End of excerpt.]
I don't understand what's going on here, and would appreciate it if
someone would explain it to me. I'm going to suddenly have to start
paying an extra $8 each month, for "the ability to make a long
distance call". Who does this go to, and what costs does it pay for?
What is paying for this now? Is this $8/month going to be optional if
I never want to make long distance calls? What if I use MCI or Sprint
or whoever exclusively? How is my ability to RECEIVE long distance
phone calls affected?
By the way, I am OUTRAGED at a 100% increase in my phone bill (you'll
notice that the part I can avoid: the $1.50 phone rental, isn't going
up) in an era where improved technology and increased competition
should be driving my phone bill DOWN. Even the gas and electric rates
aren't going up this fast, and they have a good excuse (the Arabs
raised the price of oil).
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Date: 1 Apr 1983 1157-PST
From: Lynn Gold <FIGMO at KESTREL>
Subject: Long-distance access charges
We have MCI; my father has a calling card. If there were to be a
long-distance charge, we'd want to use MCI instead of Ma Bell for
far-away calls, but to call my folks, we'd want to be able to use my
father's card.
How would the phone company enable one to do this?
(WOULD they?)
--Lynn
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From: "DRAGON::DONJON::GOLDSTEIN c/o" <SCHRIESHEIM.MITTON at DEC-Marlboro>
Date: 2-FEB-1983 10:13
Subj: Digest comment -- Local measured service fairer?
[In-real-life: Fred R. Goldstein]
The local measured service issue has been floating around the
telephone industry for a decade or so, and the recent round of plans
and arguments has a familiar ring. GTE especially uses the old line
"fair to pay for what you use", while Bell cos. talk about keeping
rates down. Politically, they think the heat is worse when they raise
basic rates (which will go way up soon anyway due to the FCC's "pure 2
access" decision) than when they charge your pants off when you call
your grand- mother down the block.
Some studies done in the mid to late 70s showed that the
fixed, usage-insensitive portion of local telephone costs were roughly
80% of the non-toll total, with incurred by local usage. A Denver
study showed that the "cost to the phone co" of local usage ranged
from <.001/min within a short-haul local rea, and less than $.03/min
on the longest local call in Colorado, 58 miles (Castle Rock to
Boulder). NY Tel's rates, though, for LMS in NY City are based on,
among other things, a study done by NYPIRG that showed much higher
costs than that in NY, but still below what most telcos ask for. The
present NYTel local usage rates are contributory (above cost) but not
hugely so.
I don't see what's so "fair" about paying more to use a
super-cheap resource, local usage, to hold down the cost of basic
service to some pitiful fraction of true cost. Let the telcos be
forced to show their true marginal costs of service, and charge
accordingly (they are mono- polies, right?, and regulated supposedly
to meet costs) if it seems worthwhile. Were that done, many LMS plans
would be dropped as costing more to administer than they take in. In
the meantime, pressure your local cable companies (if you have one --
we're still waiting for Boston to get wired) to give some competition
to telcos.
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From: "JOHN CROLL AT KIRK c/o" <SCHRIESHEIM.MITTON at DEC-Marlboro>
Posted-date: 03-Feb-1983
Subject: An anecdote from the history of Telephony
In the February 14, 1983 issue of Forbes, this anecdote is related:
Cincinnati, December 26, 1982: A Mr. A. H. Pugh, dissatisfied with the
service of the telephone company, was moved to strong language: "If
you can't get the party I want you to, you may shut up your damn
telephone!" Aghast, the phone company removed its instrument from Mr.
Pugh's home. He sued to get it restored, but the courts decided in
favor of the company. "Damn" was not to be said over the wire.
-- American Heritage
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From: "KENNETH GOUTAL at ELMO c/o" <SCHRIESHEIM.MITTON at DEC-Marlboro>
Posted-date: 03-Feb-1983
NAME-IN-REAL-LIFE: Kenn Goutal
Subject: Calling card query
Over the years, I have heard phrases like "telephone credit card"
and, lately, "Calling Card", and even seen the phone company promoting
such things. They seem to be particularly big with sales types who
make calls from random parts of the country and charge the calls to
their company. Such a use I can understand. However, a lot of the
promo literature seems aimed at just random people.
How many every folks have need of such a thing? What's the problem
with just telling the operator "Charge this to my home number"? Is
there a cost benefit? If so, how come? From the discussion lately,
it sounds like just more overhead all around. Have settled down
somewhat in recent years, I haven't done this *as often*, but I don't
recall *ever* having any trouble doing this. The closest I ever came
was being asked by the operator "Is there someone at that [home]
number that I can check with at this time?"; when I answered "yes",
the call was put through unquestioned!
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Date: 1 Apr 1983 15:06:18-PST
From: Robert P. Cunningham <cunningh@Nosc>
Reply-to: cunningh@Nosc
To: wmartin@office-3
Subject: Multi-device hookup with modems.
I have actually tried that, using 4 modems on a conference call. It
doesn't work very well. Here's why:
Each modem uses one pair of tones to send messages, and 'listens' for
a completely separate pair of tones. At 300 bps (Bell 103 standard),
that's all done with frequency-shift-keying (FSK). If a modem has no
data to send, it just puts out one of the tones constantly (the
'mark' tone). To send a bit, it changes quickly to the other tone.
Right away, there is a problem. The modem never 'listens' for the
tones it is sending...it wants to hear the other set of frequencies
instead. That's fine with just two modems, one is in the so-called
'originate' mode, the other in 'receive' mode, which just means that
one modem's sending tones correspond to the other's receiving tones.
What happens when you add a third modem is that it never 'hears' one
of the other two (tone assignments guaranteed incompatible with one of
the others). Adding additional modems make things even worse.
The way we did it was to have all the modems except one in the same
mode. That one could send to all of the others, and could hear all of
the others (but they couldn't hear each other). Think of a UN meeting
where everybody wears earphones except the speaker. Each of them can
hear him/her, but they can't hear each other---but the speaker can
hear all of them.
At least that's what we (naively) thought. And we even tried to set
up the next logical step: have the single modem (the 'speaker', that
everybody listens to) echo whatever was heard, therby broadcasting to
all of the others (trying to create a contention broadcast scheme like
the ALOHA or ETHERNET systems). Unfortunately, that didn't work.
Remember, all these modems are sending the 'mark' signal all the time.
What actually happens is that a modem locks onto one particular signal
(using a phase-locked-loop = PLL, typically). Only the strongest
signal seemed to get through in our setup. Imagine all the delegates
in the audience of that UN session mumbling all the time -- when they
had nothing to say. Only the loudest one could cut through all the
mumbling when he/she had something to say.
In reality, it is a bit more complicated, since there are small
differences in frequency (and certainly phase) between the 'mumblers',
which complicates matters a bit.
Note that true contention systems (ETHERNET, and I believe the old
ALOHAnet) are very careful only to have a carrier on the medium when a
message was actually being sent. If you can figure out how to do that
with your modems, you might have a working system (but you will
probably still need a constantly-active 'headend' repeater). On the
other hand, you will have to add addressing, etc., and at 300 bps you
will probably be disappointed with the throughput. In particular,
with a true contention system (no modem 'listens' to see if anybody
else is sending before it puts something on the line), and assuming
fairly short, random sending (no channel hogging), your throughput in
the long run is probably limited to about 18% of full-time 300 bps,
with strongest signalers having a considerable edge in getting their
messages through.
Bob Cunningham <cunningh@nosc-cc>
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Date: 1 Apr 83 20:57:47 EST (Fri)
From: UCBVAX@Berkeley (Steven M. Bellovin)
Subject: data conference calls
I suspect that your problem is modem tones. Here's the normal
sequence. Site A calls site B; site B's modem answers the phone and
responds with tone B0 (i.e., the 0-bit coming from B). Site A's modem
detects that tone, raises the Carrier Detect signal, and responds with
tone A0. B can then use B0 and B1 to talk to A; it in turn responds
with A0 and A1. Note that there are four distinct tones in use -- A0,
A1, B0, and B1 -- and that selection of which tones are used is made
based on who originated the call and who answered it.
This explains what your problem is. Assuming that you're making the
conference call manually (or do you have an autodialer that can flash
the hookswitch to get dial-tone again), each of the modems knows that
it's answering a call, and hence responds with B0/B1 and listens for
A0/A1. No one is talking A0/A1, though; furthermore, all the constant
B0 tones will interfere with any B1 tone generated.
It isn't clear to me what you should do about it, either. Your best
bet might be to get some true half-duplex modems; they know how to
monitor the line for the presence of another tone, and only send when
the line is free. Something like the Bell 202 might do (Novation
makes a cheap 202, incidentally), though I decline to guarantee it.
Note, though, that you'll need some way of telling the modem when you
want to talk; this is normally done by controlling the RS-232
Request-to-Send line and not talking until you see Clear-to-Send.
You'll also have to distinguish between Carrier Detect (which means
that someone else is actually getting ready to talk) and Data Set
Ready, which means that your modem is all powered up and connected.
Finally, you give up the ability to sense a hang-up.
--Steve Bellovin at Bell Labs, Murray Hill
mhb5b!smb@Berkeley (I think)
smb.unc@udel-relay (should still work)
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From: "REX::MINOW c/o" <SCHRIESHEIM.MITTON at DEC-Marlboro>
Date: 27-DEC-1982 08:28
Subj: RE: TELECOM Digest V2 #140
Re: the person who can't get unlimited local calling for the modem and
message units for his voice phone.
I have exactly this service from New England Tel. (In fact, I changed
when I had the modem put in.) Also, they don't list the modem number
and don't give it out at information: no charge as long as my regular
phone is listed.
If all else fails, you could always explain that the phone is being
put in so you don't get charged for your roommate's calls.
Martin Minow
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From: "KENNETH GOUTAL AT ELMO c/o" <SCHRIESHEIM.MITTON at DEC-Marlboro>
Posted-date: 05-Jan-1983
Subject: Mixed service in NH
I have a friend who lives in Manchester, New Hampshire, and I know for
a fact that he has mixed rates (unlimited on his modem line and
metered on his voice line), without having to declare one of them a
business line or anything. As some have suggested, this may be a side
benefit of living in an ESS exchange, and may not be statewide. --
Kenn
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End of TELECOM Digest
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