telecom@ucbvax.ARPA (07/29/85)
From: Moderator <Telecom-REQUEST@MIT-XX.ARPA>
TELECOM Digest Thursday, July 25, 1985 5:01PM
Volume 5, Issue 10
Today's Topics:
CCITT modems
level of telco service
re: leased data lines
10kb/s modem?
Re: TELECOM Digest V5 #9 - Telco Service Obligations
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Date: Wed, 24-Jul-85 18:23:41 PDT
From: vortex!lauren@rand-unix (Lauren Weinstein)
Subject: CCITT modems
The CCITT standard for 1200/300 bps operations is known popularly
as V22. It is VERY, VERY close to 212A standards. The differences
revolve around call setup and initial handshake issues, which can
cause some problems. Some people have modified their V22 modems
to be fully compatible with 212's, but it's unclear how the local
telecommunications authorities overseas would take to such actions if they
were aware of them.
--Lauren
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Date: Wed, 24-Jul-85 18:17:40 PDT
From: vortex!lauren@rand-unix (Lauren Weinstein)
Subject: level of telco service
Most telco tariffs regarding level of service are written in terms
of the percentage of blocked calls permitted during "busy hour"
on "normal" circuits.
There are special terms and formulas for this sort of stuff, but
I won't go into them here. No system can handle heavy local mass
calling concentrations except through blocking. If the calls
are hitting conventional prefixes, random people trying to make
random calls get blocked--causing much anxiety.
If a "high-volume" prefix is being used, blocking is done in a
systematic manner and avoids blockage of callers to/from other
areas. An example of a high-volume prefix in Los Angeles is
(213) 520, which is heavily used for radio station promotions
and call-ins. On the national level (plus Canada) AT&T's
area code (900) DIAL-IT network is a similar "controlled blockage"
system.
--Lauren
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From: crash!scotto@SDCSVAX
Date: Wed, 24 Jul 85 12:38:53 PDT
Subject: re: leased data lines
Mark,
Regarding your problem with trying to run a data circuit 2 miles,
the metallic circuits are hard to find in California, mainly because
the phone company is phasing out copper wire for fiber optics. They
also will not say whether or not service will be permanent.
Again, in California, DDS (Digital Data Service) would be the way
to go. The prices are more than competitive to analog, and the
equipment is much better. You can get a CSU/DSU (channel service
unit, data service unit) for $695.00 and it will run at 2400, 4800
9600 & 56kb switch selectable. You pay the telco for the speed you
wish to run, and they supply the clock. The one drawback, is the
installation cost, about $800 per site. The mileage fee would be
next to nothing. I would gestimate you will have a monthy fee of
under $100 with the investment of $3000.
Let me know if you would like some more information, and I will
get with you.
-- Scott O'Connell
crash!scotto@ucsd - or - crash!scotto@nosc
{ihnp4, cbosgd, sdcsvax, noscvax}!crash!scotto
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Date: Thu, 25 Jul 1985 03:03 MDT
From: "Frank J. Wancho" <WANCHO@SIMTEL20.ARPA>
Subject: 10kb/s modem?
There was a featured article in last week's InfoWorld about the
FastLink Modem. Anybody actually used a pair and can tell me if it
can transparently handle 8-bit binary data?
--Frank
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Date: Thu, 25 Jul 85 08:34 EDT
From: DuFlon.wbst@Xerox.ARPA
Subject: Re: TELECOM Digest V5 #9 - Telco Service Obligations
Around 1970, New Jersey Bell evidently had a scheme to give priority
dial tone to certain customers during network overloads. A side mounted
push button on a telephone applied what sounded like a ground to one
side of the line. I tried this out at a bank (unfortunately not during
an overload), and would guess that lines had to be specially set up for
this. I believe that the CO was a #5 X-Bar.
On a ground related note, ringback systems in some offices will give 4
short rings instead of 1 normal ring if there is excessive ground
leakage to either side of the line.
Ray DuFlon
DuFlon.wbst@Xerox.ARPA
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End of TELECOM Digest
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