telecom@ucbvax.ARPA (08/17/85)
From: Moderator <Telecom-REQUEST@MIT-XX.ARPA>
TELECOM Digest Friday, August 16, 1985 6:19PM
Volume 5, Issue 20
Today's Topics:
uniden chordless phones
Data Over Voice Equipment (DOVE)
Telstar call control system
Cellular Phone Rates
Re: TELECOM Digest V5 #19 - 976 Dial it services
Cellular "air time"
976 "applicable toll charges"
Local loop capabilities
50K baud modems and up, etc.
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Date: Thu, 15 Aug 85 19:00:40 edt
From: mgrant@umd-burble.ARPA (Michael A. Grant)
Subject: uniden chordless phones
I found this in the Baltimore Sun, I thought some of you out there might be
interested in this, so I typed it in. I take no responsibilities for
the accuracy of the information I have furnished. It is correct, to the
best of my knowledge.
-MGrant
Uniden has anounced a nationwide program whereby owners of certin Uniden and
Extend-A-Phone cordless telephones can have their handsets retrofitted with
new "slope" ringer circuitry. This modification will make the handset ring
signal come on gradually with a reduced overall sound level.
Uniden is offering this free modification because of controversy surrounding
the alleged affects of cordless telephone earpiece ringers. Most older
cordless telephones handsets ring through the earpiece, and when such units
are not used in accordance with manufactures' instructions, they may ring
directly into the ear. Some people have complained of alleged hearing
impairment associated with such accidential misuse. Medical authorities are
in disagreement as to whether this may affect hearing. Uniden has
redisigned its ringer circuitry and, to miminize controversy, is offering to
modify certain older handsets by incorporating this improved circutry and
reducing the ringer sound level.
If you own any of the following Uniden or Extend-A-Phone models, you may
have your handset retrofitted with the new "slope" ringer circutry.
Send model number and serial number to:
Slope Ringer Retrofit Center
P.O. Box 50433
Indianapolis, IN 46250
Model No. Eligible Units
------------------------------- ----------------------------------------
EX-300, EX-900, EX-1500, All units
EX-1000, EX-1100, EX-7000
EX-3000 Mfg. dates 6/82 - 8/83 excluding
serial no. 33120001 - 33130000 on 8/83
EX-3300 serial no. 33000001 - 33005000
EX-3500 Mfg. dates 1/83 - 8/83
EX-4000 Mfg. dates 6/82 - 8/83 excluding
serial no. 33067001 - 33089000 on 8/83
EX-4500 Mfg. dates 1/83 - 8/83
EX-5000 Mfg. dates 8/82 - 6/83
EX-6000 Serial no. 23000051 - 23009004 and
33000001 - 33011012
EX-7500 Serial no. 33000001 - 33003000
------------------------------
Date: Thu, 15 Aug 1985 17:23 MDT
From: "Frank J. Wancho" <WANCHO@SIMTEL20.ARPA>
Subject: Data Over Voice Equipment (DOVE)
Speaking of correct terminology, it is Data OVER Voice, which we have
been using here for a couple of years now WITHIN certain buildings.
The data portion of the lines are collected at the "entry" of the
building, run through a multiplexor to their destination, and low pass
filters pass the voice frequencies out of the buildings.
The building my office is in is too small and thus doesn't have this
service. So I can't offer first-hand experience. However, if anybody
is *really* interested, I'll see if I can get the project coordinator
to contribute his observations.
--Frank
------------------------------
Date: Thu, 15 Aug 85 20:20:54 edt
From: cbosgd.ATT!mark@seismo.CSS.GOV (Mark Horton)
Subject: Telstar call control system
The Telstar is not an AT&T product. It almost was, but it flunked
the market tests at the last minute and was discontinued. AT&T had
already manufactured lots of them, so they offered them to their
employees at a deep discount. (They were originally to list for
around $200.) I bought two - one to use and one for parts in case
the first one broke. (It hasn't, I just took the second one out
of the box tonight - see below.) So please understand that this is
not a commercial type message - the ones being offered to the public
are through liquidators and once the supply is gone, that's it.
Neither I nor AT&T care whether you buy one or not. My box and
literature say "American Bell" on them.
The Telstar is a really neat gadget if you like gadgets. It does
lots of different things, some well, some not so well. The major
function is as an answering machine, but it's really not very good
at that. It has no tape anywhere, everything is stored digitally
in RAM. When someone calls you and leaves a message, all it stores
is the date and time of the call and it has them touch tone a phone
number in. This works well if you recognize the number, but there
are times when a number just isn't enough. If it's a residence, you
need to ask for a particular person. Same for a business. Someone
left a message on my Telstar the other day, and I called them back.
(The Telstar will dial the call for you, which is nice.) It turned
out to be "Happy Valley Chicken Farms". I explained to the person
answering the phone who I was and that someone at that number had
left a message for me to call that number, and I gave the time of
the call. He had no idea who would have called. Might even have
been a prank. But it's embarrassing to return such calls if you
don't recognize the number. The number of rings before it answers
can be set from 1 to 15. When there are new messages, you are told
by a stuttered dial tone when you pick up the phone to place an
outgoing call. (If you go for a few days without placing an outgoing
call, you won't find out about the message.)
The Telstar is a box the size of a Kleenix box. It plugs into your
phone line *in series*, preferrably at the demarcation point between
the telco line and your private wiring. All phones downstream from
it can use the features. It has a speech synthesizer (it uses the TI
chip, as I understand it, the quality is quite good.) It can use either
an RJ11C jack (the dual-jack Radio Shack wall outlets are handy) or an RJ31X.
There is a membrane keyboard with 30 keys, one for each letter plus some
duplicate functions (A-J doubles as 1-0, S-Z double as fire, police, medical,
home, id code, time, date, and name/dir.) You can configure it from the
keyboard directly, and also talk to it from any touch tone phone in your
house, or from a remote phone. It has a battery backup and a clock,
so power failures aren't a problem. (When power shuts off, the relays
short the line back to the pre-telstar state.)
Another thing Telstar has is a name directory. It holds up to 30 numbers,
you punch in the name in alpha and the number. This is mainly useful to
avoid hunting for your address book; the dialing sequence is about as long
as dialing the number, so it's not useful for speed dialing. You can call
home from a remote phone to ask it for a phone number. You can key in the
name from a touch tone phone - it beeps as soon as you've keyed in enough
letters to uniquely identify the name from the set it knows. One win of
the name directory is that if someone in the directory calls and leaves
a message, when it plays back it tells you the name of who called (it
spells it out, no attempt to pronounce it) instead of giving the number.
Telstar has a few other nifty features of lesser importance. One is that
you program in three numbers for police, fire, and medical, and in 2
keystrokes you can dial them. In an emergency, they are fast to dial.
You can put a call on hold (possibly to change phones) by hitting H #,
but only if the other caller called you. (Not sure why the restriction.)
You can turn on "long distance restriction" which forbids long distance
numbers from being dialed. (There is a system "password" which you have
to enter to change this.)
You can use the phone as an intercom by dialing, say, * I 4 # (think of #
as carriage return) and hanging up; the phone will ring in burst of 4
quick rings (or whatever number you dial) until it is answered remotely,
then you pick up. You can encode different numbers, e.g. 2 means "dinner
time", 1 means "pick up an incoming call".
You can check messages, and have it repeat or call any number. It also
remembers old messages (there are about 20 messages still on my Telstar,
going back to when I hooked it up last Christmas.)
You can put a "call forward announcement" which is like call forwarding
but the caller has to dial the new number himself.
You can turn on "call screening", where the telstar intercepts incoming
calls before your phone rings at all. (You have to give a time at which
call screening turns off, so you can't leave it on by accident.) It has
the user key in their phone number. If it's in the name directory (and
optionally if you assign "special status" to one or more names, only for
special names) it will ring your phone, otherwise it just takes a message.
If you pick up for an outgoing call, it tells you it's on before you dial.
There is a "last number dialed" command to repeat it, but since you have
to type *LND# (listen to number) C, it doesn't save many keystokes, and
it only remembers one number. (In general, you can type at any point
without waiting for messages to finish.)
Anyway, this is a nifty gizmo for people who like to play with gizmos.
Since I gathered people on this list would like to play with one, and
since I have a line that isn't doing anything for a couple weeks, I dug
out the spare Telstar and hooked it up. Feel free to call, but I reserve
the right to turn it off if it starts to be a problem. I will only leave
it connected for a week or two anyway. The universal reaction I've gotten
from regular people who left a message on it is "Wow! That's a really
neat answering machine you've got!"
The number is 614-868-4276. You can do the usual "leaving a message"
thing (I won't call you back) if you like. Or hit * to get into remote
mode. The ID code is set to "1234". It will prompt you for most things,
but a list of commands and general hints is useful.
It doesn't understand dial pulse, just DTMF. In general, * gets its
attention for a command, "beep beep" is a prompt for you to type in
a command, and # is CR. Possible commands include "ND#" (name directory),
"CM#" (check messages), "CT" (check time), "CFA#" (to check or change
the call forward announcement),
I've put three names into the name directory: "me", "myself", and
"information", so you can see how it deals with the ambiguity. They
aren't very interesting.
Mark
------------------------------
Date: Thu, 15 Aug 1985 20:15:39 EDT
From: MyTH <1372804%PUCC.BITNET@WISCVM.ARPA>
Subject: Cellular Phone Rates
Here in New Jersey, I've seen cellular phone service rates of about
$25/month. Typical USE charges are what you really pay for, to the tune
of 15 to 30 cents per minute. That charge applies equally to incoming and
outgoing (local) calls. Long distance calls may be made at regular AT&T
rates, or you can use Sprint, MCI, etc.
Equipment is another matter. I don't know anything about any $500
telephone sets, but I wouldn't be surprised if they exist. Many customers
choose to rent sets for about $50/month.
Typical minimum time period for trial service with rental is about
six months, but it can range from a couple months to a couple years,
depending on which company you choose.
Roamer service can create additional billing headaches and service
problems if you're far from home, as many readers of TELECOM Digest
already realize. Most people don't bother to initiate legal action with
the FCC, but it can be a hassle...
MyTH out!
(1372804%PUCC.BITNET@WISCVM.ARPA)
------------------------------
Date: Thu, 15 Aug 85 18:26:49 pdt
From: kjd@Berkeley (Kevin Dunlap)
Subject: Re: TELECOM Digest V5 #19 - 976 Dial it services
One intresting qurk I have found in the 976 is that dialing
these numbers long distance is cheaper then dialing them localy.
Some of the same services are given in different area code 976
numbers. If I dial this service in my area code (415) it cost's me
$.50 , if I dial this same service in (212) it costs me $.20.
-Kevin
---------------------------------------------------------------------------
Kevin Dunlap kjd@berkeley.edu
UC Berkeley, CSRG ucbvax!kjd
------------------------------
Date: Thu, 15-Aug-85 18:50:48 PDT
From: vortex!lauren@rand-unix.ARPA (Lauren Weinstein)
Subject: Cellular "air time"
You're charged for all time you're on the air. As far as I know,
that includes time dialing, ringing, unanswered outgoing calls, calls
inbound to you, etc. The only thing that I don't think you're charged
for is the attempted ringing of your mobile by a landline party when your
mobile phone is not turned on or you're out of the service area.
--Lauren--
------------------------------
Date: Thu Aug 15 20:59:34 1985
From: mcb@lll-tis-b (Michael C. Berch)
Subject: 976 "applicable toll charges"
Most advertisements offering 976 services state the charge as (for
example) "55 cents plus applicable toll charges". Just where is the
toll charge TO? I live in a San Francisco suburb. If I dial a 976
number, am I charged
1) A toll charge to San Francisco (the "central city" of the
area code), normally about 15 cents ?
2) A toll charge to the actual location of the 976 service
provider (which might be anywhere in the Bay area)?
3) No toll charge?
Or does the "applicable toll charge" refer only to callers from outside the
area code, who obviously must reimburse a toll carrier for getting
their call to California?
Michael C. Berch
mcb@lll-tis-b.ARPA
{akgua,allegra,cbosgd,decwrl,dual,ihnp4,sun}!idi!styx!mcb
------------------------------
Date: Friday, 16 Aug 1985 06:32:36-PDT
From: goldstein%donjon.DEC@decwrl.ARPA (Fred R. Goldstein)
Subject: Local loop capabilities
The capacity of a local loop can be measured in analog bandwidth
(kiloHertz) OR in digital bits per second, depending upon the mode
of the loop. A standard voice loop is analog, so its capacity in
bps is only the capacity you can get using the Shannon laws,
subtracting for reality. That's why you can't find a modem faster
than 16.8 kbps. But the phone company routinely runs 3 Mbps over
the same cables, on the same poles, using T1C digital signalling.
This is a purely digital technique, not based upon modems.
T1 and T1C loops use bipolar alternate mark inversion signalling.
That's a technique where each "1" is a pulse and each "0" is
nothing. Each "1" pulse is sent the opposite polarity from the last
pulse (with a few exceptions in some versions), so that it's overall
DC avereage voltage is zero. Those of us brought up on the RS-232
limit of 9600 bps for 50 feet find this quite impressive; T1C can
go 6000 feet between repeaters, and is self-clocking to boot.
Longer distances require slower loops or repeaters. The ISDN
basic rate (2B+D, or 144 kbps) signalling scheme isn't finalized
yet, particularly since there's some question as to how it should
be run full duplex, but it will probably be good for 4-5 miles
over clean (unloaded, good condition) local loops. These loops
will not carry analog voice (i.e., Data Over Voice), but they will
carry digitized voice just fine.
Some of the telcos are interested in exploring glass local loops,
at least for some high-volume customers. The digital bandwidth
available over optical fibers is awesome. But the cost is, too,
unless you've got enough volume to make use of it. We're pulling
a private optical fiber network between DEC sites, and our 45/90
Mbps requirements don't even begin to tax the state of the art.
------------------------------
Date: 16 Aug 85 0027 PDT
From: Allan Miller <AAA@SU-AI.ARPA>
Subject: 50K baud modems and up, etc.
One piece of information that is useful in these discussions is the
Shannon-Hartley law, namely:
C = B lg(1 + S/N)
where C is the channel capacity in bits/second, B is the bandwidth in hertz,
lg is log base 2, and S/N is the signal to noise ratio. This derivation
assumes that the channel has additive white Gaussian noise.
The other useful piece of information is Shannon's second theorem, which
says that there exists some coding that can be used to transmit data arbitrarily
close to the channel capacity with arbitrarily small probability of error. Of
course, it doesn't say anything about how to make these codes.
So if the phone line bandwidth is 3KHz, then it is "theoretically" possible
to send 9600 baud with a S/N of about 7 (approx 8dB) and 50Kbaud with a S/N of
about 60,000 (approx 48dB). Note that with a perfectly noise-free line, an
infinite data rate is "theoretically" possible.
Allan
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End of TELECOM Digest
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