telecom@ucbvax.ARPA (07/29/85)
From: Moderator <Telecom-REQUEST@MIT-XX.ARPA>
TELECOM Digest Sunday, July 28, 1985 7:42PM
Volume 5, Issue 11
Today's Topics:
data line from Tech Sq. to Harvard Sq.
pay (coin) telephones
2400 baud auto-dial/auto-answer modem for $399
CCITT V.22bis / Bell 212A modems compatibility
LD carriers for 1200 baud
leased lines
News from Pacific Bell - You can now cancel Call Waiting
Fast Modems
New 9600 baud modem
Paul Baran, modem hero
Need surge protectors for phone lines
----------------------------------------------------------------------
Date: Sun, 21 Jul 85 17:48:59 pdt
From: amdcad!amd!phil@Berkeley (Phil Ngai)
Subject: data line from Tech Sq. to Harvard Sq.
Here in California the local RBOC will not give you metallic circuits
that cross Central Office boundaries. That means you can't get a 43401,
only a 3002 type circuit. Believe me, I've tried. I'm afraid you'll have
to buy real modems instead of cheap reliable line drivers.
The higher speed alternatives include DDS, T1, microwave, and infra-red,
but they are all much more expensive.
This is only my opinion and an unofficial one at that.
Phil Ngai (408) 749-5720
UUCP: {decwrl,ihnp4,allegra}!amdcad!phil
ARPA: amdcad!phil@decwrl.ARPA
------------------------------
Date: Friday, 12 July 1985 08:18-MDT
From: Henry Schaffer <decvax!mcnc!ecsvax!hes@Ucb-Vax.ARPA>
Subject: pay (coin) telephones
There was an inquiry recently about manufacturers of coin (pay)
phones, and since I just received the July issue of TELECONNECT A
Monthly Telecommunications Magazine, which primarily covers the
telephone interconnect market (phones, pbx's, accessories), and which
has a Buyers' Guide - I can give a list of manufacturers and
suppliers:
These are all working systems, for people who want to (and are allowed
to) install their own pay phones. They don't necessarily look very
much like the conventional 120B coin telephone traditionally
manufactured by Western Electric (now AT&T Tech) or GTE Automatic
Electric. (# means I saw a display ad.)
-----
Capital Tel Systems Fairfield NJ 07006 800-524-0671
Cointel Comm. # Calabasas CA 91302 818-716-5889
Communic. Mgmt. Assoc. Latham NY 12110 518-785-3559
Digitech Comm Huntsville, AL 35801 205-533-5941
Gladwin Inc. # Oakwood, GA 30566 404-536-6023
Hegge Services Redding, CA 96003 916-243-8341
Ma Best Tel. Prods N. Hollywood, CA 91607 818-760-8500
Microdevices Richardson TX 75081 214-644-8835
Northern Telecom Nashville, TN 37205 615-256-5900
Precision Comm Serv Tampa, FL 33609 813-870-0362
R-TEC Systems Bedford, TX 76021 817-267-3141
Rand of Phoenix Phoenix, AZ 85009 800-262-7263
Telephone Ext Corp Pearl River NY
Tonk-A-Phone # Spring Park MN 55384 612-471-0126
U S Telecomm # St Petersburg FL 33702 813-527-1107 (sells Gladwin)
Valcom Roanoke, VA 24013 703-982-3900
W Q Watson & Assoc Gainesville FL 30503 404-522-9246
-----
(Usual disclaimer) --henry schaffer
------------------------------
Date: Friday, 12 July 1985 18:08-MDT
From: rick@Seismo.ARPA (Rick Adams)
Subject: 2400 baud auto-dial/auto-answer modem for $399
I have spent the last 2 weeks evaluating a US Robitics Courier 2400
modem. I have beat on it pretty severly and can't find anything wrong
with it. We are buying several. I like it well enough that I will
probably buy myself one for home use.
The modem was used for uucp traffic on seismo for 2 weeks. It was used
for both dialins and dialing out. The ONLY problem I could find with
it is that if you try and call another site at 2400 baud and it can
only sync up at 1200, the modem prints "CONNECTED 1200" and then
resets the baudrate to the host to 1200 baud. I added 5 lines of code
to the dialer in uucp and have had no problems since. I consider this
to be minor.
Anyway, on to details. The GSA cost is $399 quantity 1. If you are not
on the GSA scale (i.e. if you don't buy as a US government agency),
you can still get it at this price by mentioning you heard about this
price from The Center for Seismic Studies (i.e. where I work). The
list price on this model is $895 and the regular non-GSA price is $479
(other dealers may charge more).
The modem operates at 300/1200/2400 baud (Bell 103/Bell212A/CCITT
V22.bis) in both originate and answer mode. It will fall back to 1200
from 2400, but not from 1200 to 300 in orignate mode and correctly
autobaud in answer mode. A nice (and undocumented feature) is that the
modem will detect what baudrate the computer is sending at and use
that as the dialout speed. This means you can just list the same modem
in your L-devices file 3 times with different speeds and not change
anything else. [it's simpler than it sounds if you are confused]
In orignate mode, it will detect (with a serate message for each)
ringing, busy, dialtone, and voice (and hang up on a voice).
It uses a superset of the HAYES SMARTMODEM command set. I used the
unmodified Hayes driver for a while before changing it to also handle
the USR extensions. It also claims to be able to be used with
CrossTalk, SmartCom and PC-Talk communications software, but I was
unable to test this. (I presume it will work, as it looks like a
hayes)
It does pulse or tone dialing and if tone dialing doesn't get rid of
the dialtone, it will try pulse dialing.
The warranty is 2 years from US Robotics. The dealer will also handle
warranty repairs (by sending you a working one and sending yours off
to the factory.)
The 1200 baud performance was much, much better than our Racal-Vadic
MACS dialers. We were able to connect to sites with the USR modem that
we could not get to with the Vadic modem. There was very little noise
at 2400 baud and virtually none at 1200. I successfully connected at
2400 baud to ATT, Concord Data Systems, Vadic and USR 2400 baud
modems, so there is no interoperability problem. This also worked at
2400 baud on our ITT WATS lines which are much, much noiser than ATT
WATS (then again, they are also much cheaper, you get what you pay
for). I expected it to have problems with the noisy ITT lines, but it
worked perfectly. I wasn't able to give it the acid test of trying to
use Sprint, but then nothing works on Sprint reliably...
Physically, it's 6" x 10" x 1". It's a very nice, low profile modem.
The dealer is the major east cost distributer for US Robotics and has
many units in stock. We received ours within days of placing the
order.
The $399 price is ONLY available from the following dealer. Any other
dealer will probably charge you more.
The dealer is:
Advanced Data Products, Inc.
18974 Bonanza Way (B-3)
Gaithersburg, MD 20879
(301) 424-9490
The salesmans name is:
Don Parnell
You can probably pay for the cost of the modem in the savings in a few
months phone charges.
It sounds too good to be true, but I've got a couple in the computer
room proving they are real.
---rick
------------------------------
Date: Fri, 26 Jul 85 02:29:12 EDT
From: Minh N. Hoang <MINH@MIT-MC.ARPA>
Subject: CCITT V.22bis / Bell 212A modems compatibility
CCITT (Consultative Committee [on] International Telephone & Telegraph) is
another standard-producing organization which specifies modem types, among
other things.
Starting in the middle speed at 1200 bps, the modulation schemes for
the V.22bis fallback mode (V.22) and the 212A are identical. The
crucial difference is the answer back tone which is 2100 Hz for
V.22bis and 2225 Hz for 212A. In some foreign phone system, the 2225
Hz tone causes line disconnect instead of (well... more like along with)
disabling echo suppressor. Thus with a 212A, you can call a V.22bis
(or V.22) while the reverse won't always work.
Going to 2400 bps, there's no Bell equivalence. The modems which
comply with V.22bis spec. send 2100 Hz answer back tone and they'll
work over international circuits. However, make sure the modem says
V.22bis type because CCITT does specify another 2400 bps full-duplex
type as V.26ter. They are incompatible (of course): V.22bis uses
frequency-division multiplexing to separate the transmit and receive
bands; V.26ter uses echo-cancellation to recover the receive signal
(like the V.32, yet another CCITT spec. modem which works at 9600 bps
or 4800 bps full-duplex).
Going down to 300 bps, the modulation is Bell 103 type and that isn't
compatible with any CCITT modem at all. This is strictly an American
addition to make V.22bis fully compatible with Bell 212A types.
Other considerations, since your address mentions Korea, are: the
electric company interface (plug type, voltage, frequency), the phone
company interface (modular jack for US & Canada, terminal block for
European PTTs, terminal block with ring input for Japan NTT, more?).
Also built-in features such as auto-dialer (most come with Hayes 1200
type), error protection (MNP) etc...
For companies: try skimming through Byte, Data Communications etc...
All the well-known companies (should) have a version of this
V.22bis/212A/103 compatible modem. Attempted non-exhaustive list:
Concord Data System, Codex, Microcom, Hayes, Racal-Vadic, UDS, DEC,
Paradyne, Novation, US Robotics, Team, Penril, Micom, AT&T...
As though life has been too simple... Cheers.
------------------------------
Date: Fri, 26 Jul 85 18:36:28 EDT
From: stuart%sesame.UUCP@harvard.ARPA
Subject: LD carriers for 1200 baud
I'm sure that this has been asked before, but: Could someone please send me
a list of which long distance companies are adequate for 1200 baud communica-
tion and which ones I should avoid at all costs? Thanks!
Stuart Freedman
{genrad|ihnp4|ima}!wjh12!talcott!sesame!stuart
{cbosgd|harvard}!talcott!sesame!stuart
or mit-eddie!futura!stuart
------------------------------
Date: Thursday, 25 July 1985 16:21-MDT
From: "Robert C. Lagasse" <lagasse%biomed.uucp@BRL.ARPA>
Subject: leased lines
Does anyone have any idea how much a telephone company
"leased-line" costs? Is it so much per mile? ( A leased line is a
pair of wires from one point such as a business or residance to
another site such as a repeater site or another building). These are
usually used with buglar alarm systems and commercial broadcast radio
"remotes" and I believe consist of nothing more than a pair of wires
from one site, to the phone company central office , then to the other
site with no switching or electronic intervention in between. ( Does
anybody have any ideas how many junctions the installer of such a line
has to make? I figure a minimun of three. One at the pole at one end,
one that he must call into a central ofiice to have someone make
between two big fat trunk cables, and then another at the pole at the
other end). I believe you can put a battery of, say, 10V at one site
and measure the battery voltage at the other, minus the voltage drop
due to connections and distance. By the way, does anyone know?: a)
the maximum allowed voltage on a leased line b) how many volts/mile is
usually lost, and c) maximum allowable current (do they fuse it
somewhere?).
I called the phone company and got the royal run-around. I tried
to explain what I wanted but was told of auto-ring circuits like the
taxi phones use (how much do they charge for those/month). As soon as
I mentioned that it would be for ham-radio remote control and also
possibly burglar alarm monitoring, I was referred to the
"mobile-phone" group which deal with mobile phone companies (probably
that cellular garbage) and they told me their lines cost $24.50/month
and then an additional fee for each minute of "air-time". I then
tried calling back the original office and re-explained that it would
be like a burglar alarm line, was then asked if it was for voice, I
was puzzled and said no, and was then told that burglar alarm lines
run ONLY to the police station and could not go between
residences.(when she asked me if it would be used for voice, it made
me wonder if they sell different kinds of lines , like, voice-quality,
and not voice-quality?? What good is a non-voice quality line
anyway????)
I then tried to explain that all I wanted was a pair of wires from
point A to point B but then she asked, " what kind of jack do you
need, an RJ-11C?" As you can see, I could not get past the
non-technical salespeople. What is the OFFICIAL name for this kind of
line? If there are any phone company gurus out there, H E L P!
Thank you for any and all answers.
Bob Lagasse N 1 A L G
------------------------------
Date: Sat, 27 Jul 85 22:53:34 pdt
From: unisoft!pertec!bytebug@Berkeley
Subject: News from Pacific Bell - You can now cancel Call Waiting
The little flyer in this month's phone bill tells of a new custom calling
feature that allows you to cancel Call Waiting on a call-by-call basis.
Simply dial 70 (or 1170 on dial phones) followed by the telephone number
you want to call, and for the duration of THAT CALL OR DATA TRANSMISSION,
Call Waiting will be canceled. When you hang up, Call Waiting will auto-
matically be reactivated.
Pacific Bell is making the feature available at no extra cost to Call
Waiting customers.
roger long
pertec computer corp
{ucbvax!unisoft | scgvaxd | trwrb | felix}!pertec!bytebug
[This feature has been in Boston for about 3 months. I just got
custom calling re-added to my lines after a short haitus, and
they sent me notification of it almost immediately. What they
did not tell you was that now call waiting is disable whenever
you are using three-way calling. Does anyone know if this is a bug
or a feature? My telco insists that it is a feature, and in
fact insist that you have never been able to get a call waiting
signal if you have a three-way call in progress. --JSol]
------------------------------
Date: Monday, 22 July 1985 22:13-MDT
From: Senior Gnome <sdcc3!sdcc12!wa371@SDCSVAX.ARPA>
Subject: Fast Modems
The fast modems are coming! (From the July 22 Issue of INFOWORLD)
Fastlink, a $2000 modem, transmits at ten thousand bits per second.
It is marketed by Telebit of Cupertino, CA, and DCA of Alpharetta, GA.
It supposedly is quite error free even on bad lines. It is available
now.
Concord Data systems of Waltham, MA, is planning to announce a 9600
bits per second modem by the end of the year in the same price range.
More modem to you!
Bernd UUCP: universe!milkyway!solarsys!earth!ihnp4!sdcsvax!sdcc12!wa371
ARPA: sdcsvax!sdcc12!wa371@nosc
------------------------------
Date: Tuesday, 23 July 1985 19:20-MDT
From: Mark Horton <ihnp4!cbosgd!mark@Ucb-Vax.ARPA>
Subject: New 9600 baud modem
There is an international standard for 9600 baud, full duplex, async,
dialup modems. It's CCITT V.32. However, I don't know of any
products that implement it yet.
------------------------------
Date: Thursday, 25 July 1985 18:55-MDT
From: "James A. Woods" <lll-crg!dual!ames!jaw@Seismo.ARPA>
Subject: Paul Baran, modem hero
that amazing telebit/dca 10kbit modem sure seemed like a minor miracle
(infoworld, 7/22), so i called telebit for the technical dope.
if the literature is to be believed, bad lines don't really faze the
thing. i'm sure a few usenet sites with $2300 would jump for it. is
it time to ring the death knell for CCITT modems, which, because of
noise and gross fallback strategies, never reach their max throughput?
hmm ... "packetized ensemble coding...inventor lists airport metal
detector, invention of packet switching in 1964, and co-founding of
equatorial communications (your friendly neighborhood spread spectrum
service) among his credits". no slouch here.
dca stock (telebit is private, but marketer dca is public) has risen
to around $30 of late, from about $22 a few weeks back.
oh, the dope --
- 512 carrier freqs. each modulated with either 6-bit or 4-bit QAM,
or 2-bit QPSK, depending on SNR.
- adaptive duplexing, to take advantage of the one-way burst
nature of most traffic.
- fallback in decrements of < 100 bps.
(successive rate halving of the v22 standard is the real killer
on dialups.)
- bell 103, 212a, and hayes command language compatibility
- call (800) telebit
ames!jaw
------------------------------
Date: Thursday, 25 July 1985 18:12-MDT
From: Brantley Coile <decvax!harpo!whuxlm!akgua!ganehd!bwc@Ucb-Vax.ARPA>
Subject: Need surge protectors for phone lines
We have had several modems (hayes 1200) get blasted by the phone
system at three sites. All of these sites are operated by GTE, by the
way. Is there a surge protector for phone lines?
Brantley Coile CCP
..!akgua!ganehd!bwc
Northeast Health District, Athens, Ga
------------------------------
End of TELECOM Digest
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